Mail shield - fails to connect to server

Ver 5.0.462
When I have the Mail Shield active I receive an error message on Outlook Express (0x800CCC00) and on Thunderbird it just sits there “connecting to server” getting nowhere.
If I disable the Mail Shield all is Ok.
With the Mail Shield active I have disabled all options in the “expert settings” except “Scan incoming messages” - still the same problem
Even if I disable “Scan incoming Messages” the problem still exists ( ie nothing ticked), the only solution being to disable the Mail Shield altogether
All my address are Yahoo POP3 and these show up correctly in the SSl Accounts as POP3.

These settings in Thunderbird 3 and Avast (see screenshots) work perfectly for me: