In our class environment, we have one class used primarily for Microsoft Access courses where each time you switch between 2003 and 2007 it will start reconfiguring with the installation dialog I'm sure you've seen before. It recently started happening in a second class and we are completely oblivious as to what triggered it. Of course external teachers use the classroom so it's hard to track any changes that might have happened. It happens for Access and Word, not for Excel or Powerpoint.
Both have the most recent updates (SP3 and SP2 for 2003 and 2007 respectively).
The users have no admin rights, but when we log in with local admin the same thing happens and keeps happening even after this "reconfiguration".
Another issue in these clasrooms was posted here: http://serverfault.com/questions/179520/opening-my-documents-prompts-for-credentials-in-redirected-environment I do not think both are related, but you might disagree. Feel free to let me know.