a2 email problem

In the aftermath of the TDS3 demise I started trialling a-squared with a view to a replacement, and like it a lot except that it is preventing my email clients (Barca - and also The Bat!)) from accessing my POP3 account with log error messages like this resulting:

So it errors out and no mail is delivered. Turn off a2 and the mail works fine. This occurs whether or not Web2Pop is running.

Is this a known problem? Solutions?

My system: Windows XP SP1, Pentium 4, Kerio 4, Counterspy, Nod32, RegRun, RegDefend, Ad Muncher. Email: Barca, TheBat!, Web2Pop