I can verify that the mail-stopping issue is affecting Eudora running under WinXPSP3 also. The failure to connect message coming from the ISP is consistent as of today. If Mail Shield is active, the mail doesn't get through. It applies to each of (together or separately), incoming and outgoing. It has been getting intermittently worse over the last little while, concurrent with the last update to v5. The Avast link was found in conversation with the ISP, who reported no current or ongoing mail server issues with my particular mail-server.
Further, although I have Avast setup to check for updates every two hours, I noticed no definitions update since Aug. 28. I manually forced an update check and am now operational to Sept 1. The mail-blocking issue remained after the update. The machine has been continuously on since Aug 27 in the early afternoon. (I reboot once a week). Also, ZoneAlarm has all four checks for all Avast items, including update. I do not believe that ZoneAlarm is involved.
Lastly, when loading GMail this morning in Firefox, I got the message that some of the services could not be loaded.
It is very, very difficult to crab about a free product. But a quick resolution to this issue, which seems to have generated at least six entries in the last couple of days here in this forum, I have to seriously consider my continued use of Avast.
[EDIT] I am not using SSL, simple password confirmation for this account.
GM