Boot up problem Ubuntu 11.04/11.10
 

Ubuntu 11.04 no problems for couple months after upgrade then suddenly baulked just before password entry required. Frozen screen. After a number of re-boots would eventually reach password entry I would enter password and computer would behave normally. I upgraded to Ubuntu 11.10 the boot sequence was ok for a few days then the same problem encountered in 11.04 appeared. I have found if I run memtest86 it finds no errors I then boot from it no password entry problems the computer operates normally. Anybody with any ideas how to overcome this problem.
Thanks in advance regards.

You probably need a fresh install. Going from the 10.x series to the 11.x series via upgrade can give a lot of problems. It might also be hardware related but problems from the upgrade are much more likely.