Xcode 4.0.1 "Don't have permission to view" Old project file - Help!

I recently upgraded to Xcode 4.0.1 from the last version of Xcode 3x (not sure which). Install went fine and I can open and view all my old .xcodeproj files without problems. All except one!

The error I get inside Xcode is

"The file "GCSCalculator.xcodeproj" couldn't be opened because you don't have permission开发者_Python百科 to view it. To view or change permissions, select the item in the Finder and choose File > Get info."

Obviously I've checked that and the permissions are exactly the same for all files as the ones in the projects that do open in Xcode. I changed permissions for everyone to ReadWrite just in case, to no avail. I feel I've tried everything obvious and can't seem to find anybody else with the same problem.

Anyone got any ideas about a fix or workaround? Typically it was one of the only projects that was actually completed so its very frustrating!

Thanks.

I ran into the same problem and found that clicking on the project in xcode and then switching the view to standard editor view will let you change all of the project settings. After editing the summary, info, and build settings areas it started working

Click to project-> Build Settings -> Compiler for C/C++/Objective-C -> Default Compiler. Hope it useful :D