I go to my mail icon on the desktop task bar and everything is fine. Mail opens,I do my thing and close it.I come back to it a little later and it wont open. Even if I go to the programs under the start button and try it there it still wont open.Why do you suppose this is happening?

Do a CTRL/ALT/DEL and bring up the task manager. See if it is running in the background... If it is, end the process. I've had programs not shut down all the way and then you are unable to reopen them.

Not doing it now. I think you scared it. I'll try to remember that check the next time it happens.

Maybe it just wasn't shutting down all the way and finally decided to later!