I got the exact same error when I did a new install of 4.5.5. I've had other DNN installs on the same server (including 4.5.4), and never saw this error before. I was suspicious of 4.5.5. But after looking over the release notes, it did not appear to be related to 4.5.5. It however does seem as though something (recently?) changed in DNN to make this appear on some (though probably a very small number) of systems.

For my server, the problem was, as suggested, related to permissions. Using Filemon.exe on c:\windows\temp (an excellent utility, BTW, download at: http://www.microsoft.com/technet/sysinternals/utilities/filemon.mspx), when I invoked the error, I could easily see what account was being denied access. Simply giving that account the same access as the account Network Service for the folder c:\windows\temp, solved the problem. I happen to use a different Security Account for the Application Pool. Not sure why this error is occuring now, but you may also have a similar issue.

Hope that helps. And thanks for performing the various uninstalls/re-installs. I very much wanted to avoid that, and the info you provided helped!