diff --git a/source/glest_game/ai/path_finder.cpp b/source/glest_game/ai/path_finder.cpp
index 5df68072..18baa28d 100644
--- a/source/glest_game/ai/path_finder.cpp
+++ b/source/glest_game/ai/path_finder.cpp
@@ -1,7 +1,7 @@
 // ==============================================================
 //	This file is part of Glest (www.glest.org)
 //
-//	Copyright (C) 2001-2008 Martio Figueroa
+//	Copyright (C) 2001-2008 Martiņo Figueroa
 //
 //	You can redistribute this code and/or modify it under 
 //	the terms of the GNU General Public License as published 
@@ -68,7 +68,8 @@ TravelState PathFinder::findPath(Unit *unit, const Vec2i &finalPos){
 		if(dynamic_cast<UnitPathBasic *>(path) != NULL) {
 			if(!path->isEmpty()) {
 				//route cache
-				Vec2i pos= path->pop();
+				UnitPathBasic *basicPath = dynamic_cast<UnitPathBasic *>(path);
+				Vec2i pos= basicPath->pop();
 				if(map->canMove(unit, unit->getPos(), pos)) {
 					unit->setTargetPos(pos);
 					return tsOnTheWay;
@@ -81,12 +82,15 @@ TravelState PathFinder::findPath(Unit *unit, const Vec2i &finalPos){
 				//route cache
 				Vec2i pos= advPath->peek();
 				if(map->canMove(unit, unit->getPos(), pos)){
-					path->pop();
+					advPath->pop();
 					unit->setTargetPos(pos);
 					return tsOnTheWay;
 				}
 			}
 		}
+		else {
+			throw runtime_error("unsupported or missing path finder detected!");
+		}
 	}
 		
 	//route cache miss
@@ -101,7 +105,8 @@ TravelState PathFinder::findPath(Unit *unit, const Vec2i &finalPos){
 	case tsOnTheWay:
 		{
 			if(dynamic_cast<UnitPathBasic *>(path) != NULL) {
-				Vec2i pos= path->pop();
+				UnitPathBasic *basicPath = dynamic_cast<UnitPathBasic *>(path);
+				Vec2i pos= basicPath->pop();
 				if(map->canMove(unit, unit->getPos(), pos)) {
 					unit->setTargetPos(pos);
 				}
@@ -122,6 +127,9 @@ TravelState PathFinder::findPath(Unit *unit, const Vec2i &finalPos){
 					return tsBlocked;
 				}
 			}
+			else {
+				throw runtime_error("unsupported or missing path finder detected!");
+			}
 		}
 		break;
 	}
diff --git a/source/glest_game/ai/path_finder.h b/source/glest_game/ai/path_finder.h
index b708c92f..1a82b1bd 100644
--- a/source/glest_game/ai/path_finder.h
+++ b/source/glest_game/ai/path_finder.h
@@ -1,7 +1,7 @@
 // ==============================================================
 //	This file is part of Glest (www.glest.org)
 //
-//	Copyright (C) 2001-2008 Martio Figueroa
+//	Copyright (C) 2001-2008 Martiņo Figueroa
 //
 //	You can redistribute this code and/or modify it under 
 //	the terms of the GNU General Public License as published 
diff --git a/source/glest_game/ai/route_planner.cpp b/source/glest_game/ai/route_planner.cpp
index ba583bf7..1bf0e4d9 100644
--- a/source/glest_game/ai/route_planner.cpp
+++ b/source/glest_game/ai/route_planner.cpp
@@ -404,6 +404,9 @@ bool RoutePlanner::refinePath(Unit *unit) {
 
 	UnitPathInterface *unitpath = unit->getPath();
 	UnitPath *advPath = dynamic_cast<UnitPath *>(unitpath);
+	if(advPath == NULL) {
+		throw runtime_error("Invalid or NULL unit path pointer!");
+	}
 
 	UnitPath &path = *advPath;
 	assert(!wpPath.empty());
@@ -443,6 +446,9 @@ void RoutePlanner::smoothPath(Unit *unit) {
 	PF_TRACE();
 	UnitPathInterface *path = unit->getPath();
 	UnitPath *advPath = dynamic_cast<UnitPath *>(path);
+	if(advPath == NULL) {
+		throw runtime_error("Invalid or NULL unit path pointer!");
+	}
 
 	if (advPath->size() < 3) {
 		return;
@@ -517,6 +523,9 @@ TravelState RoutePlanner::doRouteCache(Unit *unit) {
 
 	UnitPathInterface *unitpath = unit->getPath();
 	UnitPath *advPath = dynamic_cast<UnitPath *>(unitpath);
+	if(advPath == NULL) {
+		throw runtime_error("Invalid or NULL unit path pointer!");
+	}
 
 	UnitPath &path = *advPath;
 	WaypointPath &wpPath = *unit->getWaypointPath();
@@ -554,6 +563,9 @@ TravelState RoutePlanner::doQuickPathSearch(Unit *unit, const Vec2i &target) {
 
 	UnitPathInterface *unitpath = unit->getPath();
 	UnitPath *advPath = dynamic_cast<UnitPath *>(unitpath);
+	if(advPath == NULL) {
+		throw runtime_error("Invalid or NULL unit path pointer!");
+	}
 
 	UnitPath &path = *advPath;
 //	IF_DEBUG_EDITION( clearOpenClosed(unit->getPos(), target); )
@@ -584,6 +596,10 @@ TravelState RoutePlanner::findAerialPath(Unit *unit, const Vec2i &targetPos) {
 	AnnotatedMap *aMap = world->getCartographer()->getMasterMap();
 	UnitPathInterface *unitpath = unit->getPath();
 	UnitPath *advPath = dynamic_cast<UnitPath *>(unitpath);
+	if(advPath == NULL) {
+		throw runtime_error("Invalid or NULL unit path pointer!");
+	}
+
 	UnitPath &path = *advPath;
 	PosGoal goal(targetPos);
 	MoveCost cost(unit, aMap);
@@ -624,6 +640,10 @@ TravelState RoutePlanner::findPathToLocation(Unit *unit, const Vec2i &finalPos)
 	PF_TRACE();
 	UnitPathInterface *unitpath = unit->getPath();
 	UnitPath *advPath = dynamic_cast<UnitPath *>(unitpath);
+	if(advPath == NULL) {
+		throw runtime_error("Invalid or NULL unit path pointer!");
+	}
+
 	UnitPath &path = *advPath;
 	WaypointPath &wpPath = *unit->getWaypointPath();
 
@@ -737,6 +757,10 @@ TravelState RoutePlanner::customGoalSearch(PMap1Goal &goal, Unit *unit, const Ve
 
 	UnitPathInterface *unitpath = unit->getPath();
 	UnitPath *advPath = dynamic_cast<UnitPath *>(unitpath);
+	if(advPath == NULL) {
+		throw runtime_error("Invalid or NULL unit path pointer!");
+	}
+
 	UnitPath &path = *advPath;
 	WaypointPath &wpPath = *unit->getWaypointPath();
 	const Vec2i &start = unit->getPos();
@@ -775,6 +799,10 @@ TravelState RoutePlanner::findPathToGoal(Unit *unit, PMap1Goal &goal, const Vec2
 	PF_TRACE();
 	UnitPathInterface *unitpath = unit->getPath();
 	UnitPath *advPath = dynamic_cast<UnitPath *>(unitpath);
+	if(advPath == NULL) {
+		throw runtime_error("Invalid or NULL unit path pointer!");
+	}
+
 	UnitPath &path = *advPath;
 	WaypointPath &wpPath = *unit->getWaypointPath();
 
@@ -848,6 +876,10 @@ bool RoutePlanner::repairPath(Unit *unit) {
 	PF_TRACE();
 	UnitPathInterface *unitpath = unit->getPath();
 	UnitPath *advPath = dynamic_cast<UnitPath *>(unitpath);
+	if(advPath == NULL) {
+		throw runtime_error("Invalid or NULL unit path pointer!");
+	}
+
 	UnitPath &path = *advPath;
 	WaypointPath &wpPath = *unit->getWaypointPath();
 	
diff --git a/source/glest_game/ai/route_planner.h b/source/glest_game/ai/route_planner.h
index 89601d50..f9f9f2cf 100644
--- a/source/glest_game/ai/route_planner.h
+++ b/source/glest_game/ai/route_planner.h
@@ -1,7 +1,7 @@
 // ==============================================================
 //	This file is part of Glest (www.glest.org)
 //
-//	Copyright (C) 2001-2008 Martio Figueroa
+//	Copyright (C) 2001-2008 Martiņo Figueroa
 //				  2009-2010 James McCulloch
 //
 //	You can redistribute this code and/or modify it under
@@ -189,6 +189,10 @@ private:
 	bool attemptMove(Unit *unit) const {
 		UnitPathInterface *path = unit->getPath();
 		UnitPath *advPath = dynamic_cast<UnitPath *>(path);
+		if(advPath == NULL) {
+			throw runtime_error("Invalid or NULL unit path pointer!");
+		}
+		
 		assert(advPath->isEmpty() == false);
 		Vec2i pos = advPath->peek();
 		if (isLegalMove(unit, pos)) {
diff --git a/source/glest_game/type_instances/unit.h b/source/glest_game/type_instances/unit.h
index 8890f6b0..5656443b 100644
--- a/source/glest_game/type_instances/unit.h
+++ b/source/glest_game/type_instances/unit.h
@@ -105,7 +105,7 @@ public:
 	virtual void clear() = 0;
 	virtual void incBlockCount() = 0;
 	virtual void push(const Vec2i &path) = 0;
-	virtual Vec2i pop() = 0;
+	//virtual Vec2i pop() = 0;
 
 	virtual std::string toString() const = 0;
 };
@@ -160,7 +160,8 @@ public:
 #else
 	// new style, for the new RoutePlanner
 	Vec2i peek()			{return front();}	 /**< peek at the next position			 */	
-	virtual Vec2i pop()		{ Vec2i p= front(); erase(begin()); return p; }	/**< pop the next position off the path */
+	//virtual Vec2i pop()		{ Vec2i p= front(); erase(begin()); return p; }	/**< pop the next position off the path */
+	void pop()		{ erase(begin()); }	/**< pop the next position off the path */
 #endif
 	int getBlockCount() const { return blockCount; }