Help! My mail program just keeps shutting down. Can't get into it.....

I open it and can move around but in 5 seconds it closes.

I've tried disabling the accounts but I don't think it's that. Happens if I'm offline too.

I have the same issue, though I can actually use my Mail. It happens to me when I'm working in another app, then I notice that Mail has just closed, without warning and without and crash dialog ... I'm wondering if upgrading to Leopard will fix this?

Have a look at the Console app to see if there is anything interesting being written there. It's in Applications/Utilities/

Also try making a new user account, log in to that and see if it happens there as well.