Thunderbird no longer send/recv'ing mail

[dan]

Hello, all -

I've been using Thunderbird for quite a while now, and I love it.

However, every 15-20 minutes or so, Thunderbird stops sending/receiving 
mail.  If I hit the "send/recv" button, it's as if the button is not 
pressed.  If I try to send an email after that 15-20 minutes, the 
message just says "Sending Message...".  I end up re-starting 
Thunderbird 15-20 times a day.

Has anyone else had this problem, and if so, what did you do about it?

Thanks
-dant