Alas Avast - More AV hell.

[#1]

It’s not good to find myself in AV Hell I should be in AV Heaven! I have had to remove the home version of avast from two different setups today.
I tried to access my XP box drives through my network today and although I could see them I could not open them, unless I uninstalled Avast. I tried disabling all the on access providers but I had to do a full uninstall to get access again. What a pain I thought I was all sorted for security! There don’t appear to be any settings that I can use to allow my other box to access the PC through Avast.
The second PC was a friends PC who runs an application that uses a HASP dongle which somehow Avast was blocking, so I had whip Avast off and put AVG on.
I am not so bothered about that one but not being able to share drives on my own network is really annoying! Am I alone with this problem or is it a limitation of the free version?

[#2]

One setup I am involved with has two XP PCs sharing drives both ways. They also run applications that work with data on each other's drives
Peer-to-peer network via a router with a 3 port switch. Both PCs on same sub-net. No particular Avast rules in place to make it happen. Network Shield setting (which I think is the only quasi-firewall function in Avast Free) is set to High.
Each PC also runs Windows Firewall, but the main firewall functionality is in the router.
I usually come across this problem where Norton has been installed for it's anti-virus capability, but the included firewall has also been set to block access from the same sub-net. I don't think there is any way for Avast to do that even if you wanted it to.

[#3]

The XP box has only had Avast on for about a week, I installed it after using it on my Vista box and deciding I liked it.
Cleaning up? Well I uninstalled my previous AV properly. and I run ccleaner regularly, TBH I am not sure what else I should be doing to 'carefully clean up'.
My recent bad 'luck' with Bitdefender was that it clashes with other items on Vista. I think the new version was rush released. I am still happy with Avast on the Vista box.
I am trying to access the XP disks from my Vista Box but this was fine before the XP box had Avast and will work once it is removed. So I guess that will have to be the solution.