Mail freezes on startup

Hi there,

I just got my new macbook pro (equipped with OSX mountain lion) and after one week,

Mail freezes at startup.

At my old macbook I never had this problem.

I already looked up other discussions on this topic, and tried various solutions

(reinstall everything, delete mail.apple.com, delete some other files, etc.)

I am now back at where I started, still without a solution.

Also, I cannot click anything from the top menu-bar when I'm in Mail

(Not even the little apple in the left upper corner),

therefore I first have to go into another program.

The only option is to force-quit the whole thing.

I hope any of you can help me solve it, It would really help me out a lot...

Thanks on beforehand!