wierd screen flickering on external monitor

[TJMacGyver]

I suddently got a wierd flickering on the external monitor. It's the entire screen beeing kinda "skeewed" 5 cm to the right and back, very fast, in varying intervals.
But it is only the area beneath the mouse cursor, and it doesn't appear if the cursor is in the far right 5 cm of the screen.

(thinkpad X61s running vista ultimate 32
External monitor running 1600*1024@85)

The wierd thing is that it just suddently started, the only thing that I can think of, is that installed some thinkvantage stuff through sytem update the same day, but it wasn't at that point I noticed the symptoms.

I tried reinstalling Vista, but the symptoms was still there.
I found out that if I had a video running, the screen wouldn't flicker.
And if I have the internal LCD turned on, the screen won't flicker either.

It doesn't flicker at all, when I use my LCD TV as external monitor at 1360*768@60
or if I run the other screen at another resolution.