We had a client who had problems with the temp reporting folders. They weren't being deleted immediately - usually took 3 to 5 minutes. The visible symptom was that they could not run the same report twice in rapid succession.

The solution was to adjust the operating system. Windows XP offers the users the option to "index" their C: drive in order to improve the performance of file searches. As soon as that feature was turned Off, the problem disappeared.

Admittedly this doesn't sound exactly like your issue but it is worth checking.