Software :: Won't Work With Mail Screen / Doesn't Appear

I am however in IT and consider myself a Windows expert and technically competent. I have an iBook G4 running Mac OS 10.5.6. In all other respects the computer and OS seem fine. However, when I launch mail, no window appears in the screen. The menu bar at the top does switch to Mail. If I attempt to close mail at anytime, it will not close - I have to Force Quit mail. I have setup mail preferences correctly and am able to access the mail account from several other computers and iPods with POP clients. I know that it is setup correctly, because when I first installed the OS and set it up it worked. After installing several other standard software packages (iLife, iWork, Adobe, ...) mail came to be in it's present state. Unfortunately, I can't say exactly when or what change corresponded with the Mail problem. The only way to get a window to appear is to pull down "Window" and choose "message viewer". The inbox then appears. If I click "get mail", nothing appears to happen and no messages (inbox items or errors) appear. Also there is a smart mailbox called "saved mail" created (I did this when first playing around with mail) that I can't delete. I can select and perform the delete procedure, but the smart mailbox never goes away (even after reboot).

If I run "Connection Doctor", the connection and login for incoming mail server and the connection to the outgoing mail server both succeed. But again, clicking on get mail does not yield any readily observable results. I have tried sending test mail as well. There is no apparent outbox that I check so I don't know if there are messages in there, but none of the test messages make it to the recipient.

I have setup mail on a variety of systems (Windows, Linux, Unix, etc) over the years and have a thorough understanding of the workings of e-mail clients and servers.

Also, are there any other (preferably free) mac mail clients that combine the inbox, address book, and calendar?