Duplicate messages

[NRen2k5]

I'm using Thunderbird v3.0 along with WebMail v1.3.10 and Webmail-
Hotmail v1.2.29. I'm getting duplicate messages every few minutes in
Thunderbird's inbox. This seems to be happening because the messages
aren't getting marked as read and deleted when Webmail retrieves them.
This just started this morning (13 October 2010).