It is a waste of time, I have had it disabled since testing on day 1 when it was introduced as a plug-in. When active it scans hundreds of files on boot, this forces avast to also scan these actions, slowing your overall boot times.
The plug-in is effectively Lavasoft's Adaware, so if you have that already and or other anti-spyware products, this plug-in is a waste of processing effort. I would say let Outpost Pro do what it is good at the firewall and leave other plug-ins alone. That said I have the Ads, Attack Detection and DNS Cache enabled and started, the others all stopped/disabled.
I hate it when a program starts to become a suite and bloated, thankfully these plug-ins can be disabled without a problem.
Now I've had my rant, on to the problem
Firstly I have no problem accessing any avast download servers, so I don't know where you got the blocked IP list from. Perhaps it might just be blocking all avast IP because the avast.setup is a blocked application, see below.
Find the Options, Application tab and find the avast.setup entry, it may be in the blocked applications (if you inadvertently blocked it after a program update), if so Edit it and put it in the trusted applications. If it is already partially allowed or trusted, delete the entry and do a manual iAVS update in avast, this will force outpost to ask permission, accept.