I have Ubuntu 12.10 running on HP ProBook 4430s. I have been using it more than a year. This morning I switched it on, the screen got stuck before it boots - it was black and white terminal like screen with messages like kernel threads needs to be stopped etc. I waited but nothing happened. I forcibly shut it down and restarted it. This time it showed me a menu with options 1) Ubuntu 2) Advanced Ubuntu Options 3) Memory test. This screen has never showed up earlier and it would directly boot Ubuntu.
Next when I chose Ubuntu, it didn't boot and got stuck in the same screen with as earlier. I tried again this time with Advanced Ubuntu Options and it showed many kernel versions with recovery mode for each. I chose an older version and it booted eventually but not normally as it used to. I have only Ubuntu installed and no other OS. Why is this happening? What shall I do make my system boot normally as it used to? I have lots of data and can't afford a fresh installation. Shall I choose to upgrade to 13.10 which the software updater shows?