Weird problem

I can’t figure out why this is happening. When I’m online I can surf the net for awhile & then all of the sudden I get numbers in my scroll bar. After that things start smearing down the page & icons turn black. In order to stop this I have to close down my browser & reopen it. If I don’t close it soon enough it will freeze everything up. What could be causing this? I just upgraded my video card to a new one with a lot more memory & faster & this didn’t make a difference. I have a brand new LCD monitor also. Does anybody have a clue what this could be & how to fix it? I’m running Windows ME, have an AMD 1.8G CPU & 512 mb memory. Help, this is maddening!