Qt write errors on .user files - “Cannot Write File ... Disk Full?”

I have been having this problem since switching to Windows 7 ×64 where Qt Creator pops the error dialog up when it goes to write the .user files and sometimes other files. I’m currently using the open source Qt Creator 2.6.0. But this has happened with all previous versions of Qt Creator and QtSDK I had installed.

I have tracked the problem to the backup file create with the .user~ extension. This file sometimes is created in such a way that it is unaccessable. Then the next time Qt attempts to create the backup, it fails and up comes the error dialog. It instead creates backup files with the .user.xx1234 extension. When this happens, all attempts to access the .user~ are blocked and I cannot event change permissions.

With earlier versions of Qt Creator, this file was left permanently, and it seemed to occur every time I used Qt. With the latest version three things have changed. First the .user~ files are not always created with the problem, second the .user files are only updated at the end of a session (thank you) and third when the .user~ has the problem, the file disappears a couple of minutes after closing Qt?

Finally I did note that some people were having a similar problem when running multiple Qt Creator instances. I am running only one instance.