I have restored Windows Firewall to it's default state - it deletes all new rules and restores the default ones. Just to be sure, I checked and made sure that there were no rules related to avastsvc.exe -- there were not, even before the wipe. I then rebooted the computer. This has also not fixed the problem.
Independently of other issues, you are not reading correctly the suggestions.
IF you were using firewall rules, then you need to RE-CREATE them (not just delete them). For Windows built i firewall, there are no specific rules related to Avast by default.
For Avast 6.0.1289, ALL http traffic goes through avastsvc.exe (not just the browser's http traffic).
So, if you were using Avast correctly with previous versions, then setting "...well known browsers only" simply sets Avast as it was before. For better solutions, and when you already have firewall rules, the suggestion is to delete them and re-create them, including avastsvc.exe. When the firewall allows avastsvc.exe (both incoming and outgoing traffic, for full compatibility and completeness), then all http traffic is allowed.
By changing the "well known browsers only" setting several times (and saving), you might be "solving" a potential configuration problem in the ini file of Avast.
By rebuilding the firewall rules, you are assuring that the latest version of avast (avastsvc.exe, in this particular context) is also allowed. Rebuilding anew firewall rules reduces conflicts (because in some cases, the firewall doesn't recognize the updated executable file as valid).
If all that is not enough, from Avast point of view the simplest workaround is to run the removal utility under Windows Safe Mode (
http://www.avast.com/uninstall-utility) so to avoid any potential conflicts. In case this is really needed, I would suggest removing all previous versions of Avast too (reboot again into Safe Mode to run the removal utility again, selecting the previous version of Avast).
Then, under Normal Mode, reinstall the latest Avast version, REBOOT immediately, rebuild firewall rules (IF necessary), configure Avast and retest.
But, that is valid if Avast is the only security tool EVER installed in the system. You should remove other remnants of other security tools that were installed before (for partial a list see
http://thewebatom.net/uninstallers/security-software/).
Some other users have been successful in making it work (without having web shield completely disabled). As
craigb suggests, each system might be different and Avast web shield might not be the only problem, Some interaction with older / other security tools might be part of the problem, and the problem with the game is only showing you that there is some remnant conflict.