diff --git a/src/map/IMG/mapdata.cpp b/src/map/IMG/mapdata.cpp
index 8f6e06b2..a72cb818 100644
--- a/src/map/IMG/mapdata.cpp
+++ b/src/map/IMG/mapdata.cpp
@@ -13,14 +13,14 @@ bool MapData::polyCb(VectorTile *tile, void *context)
 {
 	PolyCTX *ctx = (PolyCTX*)context;
 	tile->polys(ctx->rect, ctx->zoom, ctx->polygons, ctx->lines,
-	  ctx->polyCache);
+	  ctx->polyCache, ctx->lock);
 	return true;
 }
 
 bool MapData::pointCb(VectorTile *tile, void *context)
 {
 	PointCTX *ctx = (PointCTX*)context;
-	tile->points(ctx->rect, ctx->zoom, ctx->points, ctx->pointCache);
+	tile->points(ctx->rect, ctx->zoom, ctx->points, ctx->pointCache, ctx->lock);
 	return true;
 }
 
@@ -45,7 +45,7 @@ MapData::~MapData()
 void MapData::polys(const RectC &rect, int bits, QList<Poly> *polygons,
   QList<Poly> *lines)
 {
-	PolyCTX ctx(rect, zoom(bits), polygons, lines, &_polyCache);
+	PolyCTX ctx(rect, zoom(bits), polygons, lines, &_polyCache, &_lock);
 	double min[2], max[2];
 
 	min[0] = rect.left();
@@ -53,14 +53,12 @@ void MapData::polys(const RectC &rect, int bits, QList<Poly> *polygons,
 	max[0] = rect.right();
 	max[1] = rect.top();
 
-	_lock.lock();
 	_tileTree.Search(min, max, polyCb, &ctx);
-	_lock.unlock();
 }
 
 void MapData::points(const RectC &rect, int bits, QList<Point> *points)
 {
-	PointCTX ctx(rect, zoom(bits), points, &_pointCache);
+	PointCTX ctx(rect, zoom(bits), points, &_pointCache, &_lock);
 	double min[2], max[2];
 
 	min[0] = rect.left();
@@ -68,9 +66,7 @@ void MapData::points(const RectC &rect, int bits, QList<Point> *points)
 	max[0] = rect.right();
 	max[1] = rect.top();
 
-	_lock.lock();
 	_tileTree.Search(min, max, pointCb, &ctx);
-	_lock.unlock();
 }
 
 void MapData::load()
diff --git a/src/map/IMG/mapdata.h b/src/map/IMG/mapdata.h
index e3c0fd02..7959cf2f 100644
--- a/src/map/IMG/mapdata.h
+++ b/src/map/IMG/mapdata.h
@@ -105,27 +105,30 @@ private:
 	{
 		PolyCTX(const RectC &rect, const Zoom &zoom,
 		  QList<MapData::Poly> *polygons, QList<MapData::Poly> *lines,
-		  PolyCache *polyCache)
+		  PolyCache *polyCache, QMutex *lock)
 		  : rect(rect), zoom(zoom), polygons(polygons), lines(lines),
-		  polyCache(polyCache) {}
+		  polyCache(polyCache), lock(lock) {}
 
 		const RectC &rect;
 		const Zoom &zoom;
 		QList<MapData::Poly> *polygons;
 		QList<MapData::Poly> *lines;
 		PolyCache *polyCache;
+		QMutex *lock;
 	};
 
 	struct PointCTX
 	{
 		PointCTX(const RectC &rect, const Zoom &zoom,
-		  QList<MapData::Point> *points, PointCache *pointCache)
-		  : rect(rect), zoom(zoom), points(points), pointCache(pointCache) {}
+		  QList<MapData::Point> *points, PointCache *pointCache, QMutex *lock)
+		  : rect(rect), zoom(zoom), points(points), pointCache(pointCache),
+		  lock(lock) {}
 
 		const RectC &rect;
 		const Zoom &zoom;
 		QList<MapData::Point> *points;
 		PointCache *pointCache;
+		QMutex *lock;
 	};
 
 	const Zoom &zoom(int bits) const;
diff --git a/src/map/IMG/vectortile.cpp b/src/map/IMG/vectortile.cpp
index 3435e65c..814b6a6a 100644
--- a/src/map/IMG/vectortile.cpp
+++ b/src/map/IMG/vectortile.cpp
@@ -102,15 +102,17 @@ void VectorTile::clear()
 
 void VectorTile::polys(const RectC &rect, const Zoom &zoom,
   QList<MapData::Poly> *polygons, QList<MapData::Poly> *lines,
-  MapData::PolyCache *polyCache)
+  MapData::PolyCache *polyCache, QMutex *lock)
 {
 	SubFile::Handle *rgnHdl = 0, *lblHdl = 0, *netHdl = 0, *nodHdl = 0,
 	  *nodHdl2 = 0;
 
-	if (_loaded < 0)
-		return;
+	lock->lock();
 
-	//polyCache->lock.lock();
+	if (_loaded < 0) {
+		lock->unlock();
+		return;
+	}
 
 	if (!_loaded) {
 		rgnHdl = new SubFile::Handle(_rgn);
@@ -119,7 +121,7 @@ void VectorTile::polys(const RectC &rect, const Zoom &zoom,
 		nodHdl = new SubFile::Handle(_nod);
 
 		if (!load(*rgnHdl, *lblHdl, *netHdl, *nodHdl)) {
-			//polyCache->lock.unlock();
+			lock->unlock();
 			delete rgnHdl; delete lblHdl; delete netHdl; delete nodHdl;
 			return;
 		}
@@ -170,19 +172,24 @@ void VectorTile::polys(const RectC &rect, const Zoom &zoom,
 		}
 	}
 
-	//polyCache->lock.unlock();
+	lock->unlock();
 
 	delete rgnHdl; delete lblHdl; delete netHdl; delete nodHdl; delete nodHdl2;
 }
 
 void VectorTile::points(const RectC &rect, const Zoom &zoom,
   QList<MapData::Point> *points, QCache<const SubDiv *,
-  QList<MapData::Point> > *pointCache)
+  QList<MapData::Point> > *pointCache, QMutex *lock)
 {
 	SubFile::Handle *rgnHdl = 0, *lblHdl = 0;
 
-	if (_loaded < 0)
+	lock->lock();
+
+	if (_loaded < 0) {
+		lock->unlock();
 		return;
+	}
+
 	if (!_loaded) {
 		rgnHdl = new SubFile::Handle(_rgn);
 		lblHdl = new SubFile::Handle(_lbl);
@@ -190,6 +197,7 @@ void VectorTile::points(const RectC &rect, const Zoom &zoom,
 		SubFile::Handle netHdl(_net);
 
 		if (!load(*rgnHdl, *lblHdl, netHdl, nodHdl)) {
+			lock->unlock();
 			delete rgnHdl; delete lblHdl;
 			return;
 		}
@@ -223,6 +231,8 @@ void VectorTile::points(const RectC &rect, const Zoom &zoom,
 			copyPoints(rect, pl, points);
 	}
 
+	lock->unlock();
+
 	delete rgnHdl; delete lblHdl;
 }
 
diff --git a/src/map/IMG/vectortile.h b/src/map/IMG/vectortile.h
index 9e617434..9f0a4214 100644
--- a/src/map/IMG/vectortile.h
+++ b/src/map/IMG/vectortile.h
@@ -29,10 +29,10 @@ public:
 
 	void polys(const RectC &rect, const Zoom &zoom,
 	  QList<MapData::Poly> *polygons, QList<MapData::Poly> *lines,
-	  MapData::PolyCache *polyCache);
+	  MapData::PolyCache *polyCache, QMutex *lock);
 	void points(const RectC &rect, const Zoom &zoom,
 	  QList<MapData::Point> *points, QCache<const SubDiv*,
-	  QList<MapData::Point> > *pointCache);
+	  QList<MapData::Point> > *pointCache, QMutex *lock);
 
 	static bool isTileFile(SubFile::Type type)
 	{