hangs after downloading mail


I am running OSX on a iMac DV-SE 500

The first time I run after I start-up my Mac and connect to my ISP (via a 56k modem connection) it logs in and downloads from my server fine but 80-90% of the time once the messages are removed from the server I will then get the "spinning ball of death". This problem continues until I force-quit. After that I can re-start mail and it behaves correctly. Occasionally this problem re-occurs if I shut down mail and re-start during a session but it mostly happens on first connect.

At first I thought it was something to do with indexing but I have tried fiddling with the indexing settings to no avail. Anyone have any ideas as to what could be wrong? I can deal with it as no mail appears to be lost but it is a pain to have to force-quit almost every time.

BTW I have tried looking at the Console log but there are no hints there either. Thanks!
Could you give me your config (dHCP or manual)?
I can connect to my ISP via my internal modem but can't see the connection?