ML Issues--Can Anyone Help?

I have a new iMac. We upgraded to Mountain Lion with no problems. With this latest software update, version 10.8.2 we started to have some problems.

1. When you go to open iTunes, it won't open and you get the round wheel. Once this happens, I am unable to select anything on the top bar like restart the computer. When I go into my wife's profile it does the same thing. At this point, the only way to restart is to power off the computer with the button in the back. ITunes will open when the computer has been first restarted but once it has been up for a while it does this.

2. Mail has issues with our Yahoo account. This worked flawless before the upgrade. About half of the time now, it pops up saying the password is incorrect for the account. If I try later sometimes it works and sometimes it doesn't. I read that you have to upgrade Yahoo mail for it to work properly. I paid for the upgrade and am having the same issues.

Not sure what these issues have to do with the new software update but that's when all of this started. Any help with this would be greatly appreciated as I have no idea what is going on!