What is actually happening: When I boot up, and right before it is suppose to prompt me for login (in GNOME), my screen just goes blank and flickers. When it flickers, it flickers into the command line login, but then after a second or two, it goes blank I again. I also see my num lock light turning on and off at the same time I see it flicker into the command line login prompt. What is happeing here?

Here's what happen before all this started to happen:
I tried to install new memory in the the PC. I have an older PC that still uses EDO (simm) RAM. When I installed it, the computer would boot up. At first it looked like it was trying (by seeing the scripts scroll on the screen), but it eventually failed. I tried to boot the system into Win98 (i run a dual boot), but it also fails there. Actually, it boots up all the way to the login of WIn98, and once you login and you start to here the Win98 startup audible, but then computer shuts off and tries to reboot again.

Anyhow, this caused an improper shutdown in both Win98 and Linux (of course). When I decided to remove the NEW RAM and just stick with the old memory that was in there, I booted up into Win98 and it booted up fine (after doing scan disk of course). Then I booted up in Linux, and of course I got the Scan Disk happeing in there too, and it found some "inode" not correct (or something like that...you know that stuff you get when you don't shutdown properly and you have to do FSCK). Well I did FSCK and it run like normal and fixed everything it needed to fix. When I rebooted linux after FSCK, linux would boot up to the point where I am suppose to see the GNOME login prompt. Then it goes blank. When I move the mouse, I notice the screen flickers and when it flickers, sometimes it will stay on and it displays command line login. If I can get the that to stay on long enough, I can actually login. But it will soon go blank again. And you can get the flickering again by moving the mouse.

What has happened here? Has anyone had this kind of experience before??? PLease help!