I've been struggling with a quite annoying issue on my personal computer . I run both Windows 8 and Ubuntu 12.04 on this particular machine, and the issue I'll describe next presents itself exactly the same way regardless of what operating system I boot to.
About 2 out of 3 times I turn on this computer, it will freeze during the OS loading/user log in phase. Often times it will allow me to login, but it will freeze within a minute or so. Once the computer freezes, the only solution is to physically force it to shutdown.
I initially thought this could be a driver problem, but the fact that this happens on both windows and linux probably proves that theory wrong. I also updated all drivers and the problem persists.
Note that if the computer does not freeze within the first minute after the OS loads, it will not freeze at all. I can use it for days and it will not freeze.
I'll be happy to hear any suggestion of what could be the cause of this problem.