Using the Microsoft provided way to delete temporary internet files (at least on version 6) does not always delete all the files.
Using Windows Explorer to delete them works, but why doesn't the tools->options->delete temp files work? It spends some time doing something?
I was just helping someone who is trying to use an application I wrote to clear their cache using the tools menu method and it didn't make any difference. Deleting the temp files using Windows Explorer (temp file folder under the user's Local Data folder) allowed the application to function properly. Very frustrating.