Erik Scrafford's workaround for http://code.google.com/p/route-me/issues/detail?id=137

+//
+//  RMCountedSet.h
+//
+// Copyright (c) 2010, Route-Me Contributors
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are met:
+//
+// * Redistributions of source code must retain the above copyright notice, this
+//   list of conditions and the following disclaimer.
+// * Redistributions in binary form must reproduce the above copyright notice,
+//   this list of conditions and the following disclaimer in the documentation
+//   and/or other materials provided with the distribution.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+// CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+// POSSIBILITY OF SUCH DAMAGE.
+
+#import <Foundation/Foundation.h>
+
+
+@interface RMCountedSet : NSCountedSet {
+
+}
+
+@end

+//
+//  RMCountedSet.m
+//
+// Copyright (c) 2010, Route-Me Contributors
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are met:
+//
+// * Redistributions of source code must retain the above copyright notice, this
+//   list of conditions and the following disclaimer.
+// * Redistributions in binary form must reproduce the above copyright notice,
+//   this list of conditions and the following disclaimer in the documentation
+//   and/or other materials provided with the distribution.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+// CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+// POSSIBILITY OF SUCH DAMAGE.
+
+#import "RMCountedSet.h"
+
+// Workaround for changed behavior of NSCountedSet in os4.0 beta1&2
+// it used to always retain the first object added
+// new behavior is to replace that object with the one passed into
+// addObject: and removeObject:
+// this is a problem for us because of the dummy tiles being added/removed
+// that don't actually contain the same data as the real tile objects
+// even though isEqual: will return true.
+
+@implementation RMCountedSet
+
+-(void)addObject:(id)object
+{
+  id objectToAdd = [self member:object];
+  if ( ! objectToAdd )
+    objectToAdd = object;
+  [super addObject:objectToAdd];
+}
+
+-(void)removeObject:(id)object
+{
+  id objectToRemove = [self member:object];
+  if ( ! objectToRemove )
+    return;
+  [super removeObject:objectToRemove];
+}
+
+
+@end

@@ -32,6 +32,7 @@
 #	import <Cocoa/Cocoa.h>
 #	import <Cocoa/Cocoa.h>
 #endif
 #endif
 #import "RMTile.h"
 #import "RMTile.h"
+#import "RMCountedSet.h"
 
 
 @class RMTileImage;
 @class RMTileImage;
 @protocol RMTileSource;
 @protocol RMTileSource;
@@ -49,7 +50,7 @@
 	IBOutlet id delegate;
 	IBOutlet id delegate;
 	id<RMTileSource> tileSource;
 	id<RMTileSource> tileSource;
 
 
-	NSCountedSet *images;
+	RMCountedSet *images;
 }
 }
 
 
 -(id) initWithDelegate: (id) _delegate;
 -(id) initWithDelegate: (id) _delegate;

@@ -46,7 +46,7 @@
 	
 	
 	tileSource = nil;
 	tileSource = nil;
 	self.delegate = _delegate;
 	self.delegate = _delegate;
-	images = [[NSCountedSet alloc] init];
+	images = [[RMCountedSet alloc] init];
 	return self;
 	return self;
 }
 }