I use the Avast 8.1483 free version on several computers.
I do the (hobby) administration of the families computers.
All in all I had a mixed situation:
1 Computer Win 8 x64 Pro; AMD G880 Chipset; works perfecly
1 Computer Win 7 (32) Pro; Very Old Intel Chipset 865PE; work perfectly
1 Computer Win 8x64 Pro; Intel P45 Chipset; Multi User; Do a permanent loop at log-in screen
1 Laptop Win 8x64 Pro; Intel Chipset; Multi User; Do a permanent loop at log-in screen
Uninstall & reinstall (with and without aswclear.exe) do not change the behaviour at the problematic PC.
After uninstall (in safety mode) both computer runs without any problems.
Hope next Version will fix this issue.