Actually, despite my earlier reply it seems that the problem is persisting, and I don't think this is what's happening in my case. There's one particular file which is having problems. There is only one file with that name anywhere on this machine, and Xcode is the only program that I ever open it with. Nevertheless, I intermittently get messages that "another program" has modified the file, and do I want to overwrite it or not. It seems that Xcode is somehow getting out of sync between (I think) the file open in a dedicated window and the same file as viewed in the build results window. Do you have any further thoughts as to how I might be able to make this issue go away?