12.04 used to work just fine a month ago. Since August, I installed all of the available updates. Since then my mac-pro is acting weird. If I restart the computer, the screen gets stuck in the purple back ground without any texts. Then if I restart again, I can choose what versions of linux I want to run. If I select 3.2.0-31-generic, the machine gets stuck in a state of blinking cursor. If I boot again to run 3.2.0-31-generic recovery mode, the machine gets stuck in a "..... memory freed End of Stack" mode. I can't boot through this kernel. I have to choose an older version of linux like 3.2.0-12-generic to boot into my mac pro, but I have too boot twice to get into this version. I was wondering --if you could provide me a solution to boot the 3.2.0-31-generic version. -- if you could provide me a solution to boot into any version the first time I restart. (Usually I have to kill the first restart) --- If there is an option in linux to choose what version I want to run every time I restart so that I don't have to choose everytime.

Thank you