Mail app will no longer check .mac .me mail

Everything was fine until yesterday's Mobile Me shambles - which stopped me from checking or sending .mac. or.me from all of my devices/computers. Today I can both send and recievce in iPad and iPhone, but on my Mac Mail app refuses to play ball, and won't check/download new Mobile Me mail.

I have tired retyping the password in preferences, but to no avail.

Can anyone tell me how to get Mail app playing well with Mobile Me again?