The only thing I've found that fixes the first problem is deleting the Battle.net folder in my users folder, though the problem reappears every few weeks. And the log-in problem's only fix is to restart the computer, as far as I've found. I recently heard that Blizzard stopped support for my OS version - could that be the root of my problems? - or do you think it's a virus or something like that? I've run scans with nothing found, but that doesn't necessarily mean that nothing's there.
I'm running Mac OS X 10.6.8, with 4 gigs of RAM and a 2.4 GHz Intel processor. I greatly appreciate any insight into this matter.