I've prepared two workspaces (one from XCode and the other one from Visual Studio Express 2005) that reproduces my current situation. Although the code and assets are duplicated for each workspace, they are the exact same files. I've renamed the png files to "pnh" so that XCode doesn't reduce its quality before putting them on the application bundle.
Any suggestion about how to solve this would be really appreciated

Thanks in advance for your help!
--Nacho