Ubuntu 9.04 freezes right before login screen
I'm having a strange problem with my system that I would appreciate your help on.
My system has been working quite well for a long while with Ubuntu 8.10 then at some point after installing certain update (I'm not sure which one is it). The box started to freeze when booting right before the login screen (I use GUI).
I have made a fresh installation for Ubuntu 9.04, which I thought it had solved the problem, but few hours later I faced the same problem.
Now what happens is, some days I manage to start the box, and some days I just can't regardless how many trials I give...
I have run a memory test which showed no errors. I also changed my display card, removed the display driver and installed it all over again. Yet the problem is still there.