Up date problem

I have re installed Fedora 18 from a DVD I cut. This has kernel 3.6.10-4 FC18 X86 64 bit.
The machine on which it installed works fine with no problems that I have come across.

I then did an update. On reboot the machine started normally till it got to the point where the Log in screen would be shown but all I get is a screen with diagonal lines. I can not switch it to a terminal screen and log in as root. Everything seems to be frozen and t have to hit the reset or OFf buttons. This was for Kernel 3.8.3.201

I than waited till another up date was available and tried to do another update from kernel 3.6.10-4. This updated kernel being 3.8.3.203. The result being the same as described above.

I did notice that the last item on the screen that can be displayed during the boot process showed that the last time to show "(OK)" before the log screen would have displayed was "Started Account service"

At this point I re installed the DVD again checked 3.6.10-4 kernel was working fine then did an update using Yum. The kernel on reboot was 3.8.3-203 but I get the same results as indicated above.

Software fedora 18 64 bit
1 Gb RAM
80GB hard drive
ASUS M2N8-VMX mother board
on board graphics NVIDIA GeForce 6100 no NVIDIA drives installed

Any ideas as to how to fix Please.