A detailed Microsoft ‘apology’ is available here: http://support.microsoft.com/kb/823196
The error is caused by the XmlSerializer and looks like this:
Could not find file 'C:\Users\Administrator\AppData\Local\Temp\1\<random numbers>.dll'
You may see this error in applications that run with your personal user account. It occurs because your user account may not have the necessary ‘full control’ permission on the temp folder and all subfolders.