The file you are trying to save (%s) is modified in memory and has also changed on the server. Your source control system ...

The file you are trying to save (%s) is modified in memory and has also changed on the server. Your source control system will get the latest version of the file when you check it out. This means that check out at this time is not safe. You can either overwrite the file without checking it out or save the file under another name. In either case, you must merge the two sets of changes manually later.