I have this same problem, which is why I just came here and registered. I'm running 4.6.623 free edition, with Zone Alarm free edition. I'm using Internet Explorer's latest version, and XP Home. I did recently add SP2 to my OS, I hope it's not the problem, because it's a bear to uninstall. I've noticed there are a fair number of protection programs that conflict with it in some way.
Recently I've had problems with downloads from certain sites not coming through unless I disable my protection, and certain sites not fully loading without doing so. At first I thought it was mostly to do with the firewall, but tonight I tested the Avast to see if just disabling that worked, and found it to be the cause of the problem.
I can log on to that Verizon site you mentioned though, with the Avast running, so it may not be a good example to test this problem with. I'm using Qwest DSL, I don't know if that has anything to do with it, just thought I'd mention it.
This is the first problem I've ever had with this antivirus, and it's got me feeling vulnerable, especially when logging on to ad based forums, or downloading very large files.
I may just take a chance on that beta you mentioned, do you remember the name of the thread it was located in by any chance? Thanks