Mac Mail application not working

Hey everyone-

Suddenly my Mac Mail application has stopped responding. I click on
the application and it will not open. All of my other applications are
working fine. I am running OS 10.3.9.

Does anyone have any suggestions?

Thanks!

that's pretty nuts, but it has happened to me before and I run 10.3.9 as well.
It would not respond what so ever, I even download Thunderbird because I just gave up.

I tried to just shut down my powerbook at one point and when I powered it back on it worked again.

go figure, can't explain

Try using something like this: http://www.jimmitchelldesigns.com/yasu.html

Clear all the system, font and user caches. If they get corrupt, weird things can happen (I couldn't drag and drop in the Finder back in 10.2 once...).