Problems with Mail with my new iMac

I just bought a new iMac and had all my data from my old PowerBook G4 transferred to it. Everything seems to be working well except for Mail. I can't see any messages whatsoever, either in my inbox or in the folders I use to organize my messages (the folders are visible but no emails inside). Through Finder, I can see that all the data is there-- In fact, I can even read individual messages in CoverFlow. (I use Gmail POP but download everything to my computer, I don't leave anything on the server.) However, if I doubleclick on an email message, it switches to Mail as if something is going to open, but nothing does. Also, Mail isn't responding to Quit. I have to use Force Quit.

Any idea what's going on? I know there's a TON of messages to keep track of but my old computer was managing just fine. I tried reindexing the messages by dragging the "Envelope Index" folder to the desktop, but nothing changed.

Okay I found my problem addressed in this thread:

http://www.mac-forums.com/forums/os-x-applications-games/135061-macmail-wont-import-function.html

Thanks for the ideas, I think I will be able to get it to work now. I deleted the file and was able to start anew, then was able to import mailboxes from where they were.

Unfortunately I've managed to delete the mailbox data but I still have it from my other computer so I'll be able to fix it with a little time.

Thanks.