I have been working away at same iPhone game development.
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.
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.
ocos2d: WARNING: format is not supported for CCSpriteFrameCache addSpriteFramesWithDictionary:texture: