Others may not experience the same problem but the other day I had to disable the AutoFill function on Safari.
It was over-riding my dotMac account user name & kept me from accessing my homepage, iDisk, etc.
The Apple tech person acknowledged that some (read many!) have had pblms with the new beta version's AutoFill.
As soon as i went in to Safari prefs, unchecked all 3 boxes in AutoFill, re-set my password, I was ok again & could get back on my dotMac page.