I have similar issues: Avast console (on SBS 2003) pushed out V7 of the Managed client to several workstations. Those that were notebook computers, runnng Avast V7, suddenly could not save any files to the local drive or netwrok shares. I remove Avast and suddenly all functions normally.
So for now, my solution is to remove Avast from notebook computers that have V7. that leaves them unprotected until Avast comes out wiht an update that will work properly.