Not used to posts. So here goes for third time!!!
Retrospect 7.6.111
XP sp3
Avast antivirus.
After hours and hours of peering at slow screen.
It fits in with rollback and replacing windows file.
I fixed my almost identical problem by using this patch - http://public.avast.com/~kurtin/patches/#ap20111707002
It came from this thread that i found - http://forum.avast.com/index.php?topic=81135.45
I'm running a backup at the moment all running smoothly. Remember to reboot after placing patch. Nodoubt Avast will sort this at next prog update.