I have been working away at same iPhone game development.
I found a nice sprite sheet editor zwoptex: http://zwoptexapp.com which is compatible with the engine I was using cocos2d: http://code.google.com/p/cocos2d-iphone/
Little did I know there was some version issues between the exporter and the engine. Zwoptex exports a png and a plist that contains all the meta-data for the sprite sheet. If you are getting the bellow mentioned error you might be reading online various suggestions like installing older versions of zwoptex or a new versions of the engine.
Solution:
As it turns out all you have to do is un-check rotate from inside zwoptex publish the files. Edit the plist generated by zowptex and change the root>>metadata>>format number from 2 to 1 save clean your build recompile and your done.
cocos2d error:
ocos2d: WARNING: format is not supported for CCSpriteFrameCache addSpriteFramesWithDictionary:texture:
Full Error:
But why this solve the problem? Whats the root cause?
Thanks alot!!! 😀