Outlook 2003: Error receiving messages typically with misformed headers

[Mike]

Increasingly, I receive the following message when I use
Outlook to receive messages from my ISP, ATT Global
(attglobal.net). When I logon to the Web mail page, I
typically find a spam message with a bad header, or some
parameter in the message in error. I delete the message,
and all is well.

Unfortunately, Outlook stops, and until I manually go
onto the ISP and delete the message, the Send/Receive
function is useless.

Any ideas?

Error message from Outlook follows:

Task 'ATT Global - Receiving' reported error
(0x800CCC0F) : 'The connection to the server was
interrupted. If this problem continues, contact your
server administrator or Internet service provider (ISP).
The server responded: +OK'