@ Harry_P
Sorry, but I recommend installing avast first, so that when Outpost is installed it detects avast and asks if you have it installed (answer yes). That way it will disable the Outpost anti-spyware and web-control modules so as not to conflict with avast's anti-spyware functionality or its web shield.
I have not excluded the Outpost program folder, I just acknowledged I did on the prompt. The only file that I exclude in the avast File System Shield (Expert Settings, Exclusions) belonging to Outpost was the C:\Program Files\Agnitum\Outpost Firewall Pro\wl_hook.dll file.
Recently after clean reinstalls of avast and the use of the 6.0.1035, I neglected to re-enter this exclusion and I have had no problem in that regard either (just re-entered it) and never had a problem with op_mon.exe.