Curious Mail Problems

Hey there, I've just upgraded to Leopard and I have some strange Mail problems.

- When I click the dock icon Mail opens, but nothing happens. I have to manually open a Mail window in the taskbar.
- All my mails are gone, when I go to my library folder I still see them, but they're not in Mail.
- I use GMail, when I send myself a message from gmail.com I don't receive it in Mail.
- Import and rebuild are greyed-out.
- Quitting Mail doesn't do anything, I have to force quit.

Macbook Pro
2.33 C2D
OS X 10.5.6

 

It seems I've already solved the issue, deleted the com.apple.mail.plist file in Library -> Preferences. Everything works fine now..