Explorer hanging after installing IE6sp1

After installing IE6sp1 (this has happened on all of the office PC's I've
tested) the following actions will cause Windows Explorer to hang for 30-60
seconds any time you do a file delete, etc.:

Open Windows Explorer
Open a browser window (eg msn)
Copy a large directory from one drive to another (eg OpenOffice1.1.3 or
similar)
Flip focus to browser, open anotherbrowser window.
While copying the directory, delete the target directory.
Resume copying when prompted to re-create the target.
Flip focus to browser windows, then back to explorer.

Doing this a few times will eventually hang Windows Explorer. From then on,
any time you try to delete a directory, Windows Explorer will hang for about
30-60 seconds. No crashes, no error messages. Shutting it down and restarting
it makes no difference.

This behaviour was NOT reporducible on a machine running IE5.0, until I
upgraded it to IE6sp1.

Any ideas?

Thanks in advance,

Zip