Drivers window keeps sticking!!!! HELP!!

Hello, i've got a 1999 A6 AVANT 2.8 QUATTRO.
My problem is: my driver's door window, every so often either goes up very slowly or goes up so far, then the safety sensor kicks in and drops the window.

Is this a sign of the cable breaking, or is it just a case of needing some lubrication on the window runners?
Any help would be great.
CHEERS FRANK.

Get rid of that crappy green text man - it hurts my eyes.

Anyhow, You need to clean out the runners - a bit of silicon lube wouldn't go amiss either.

Hi, sorry about the green text:(, I was hoping that was all i had to do. I had a horrible feeling i was going to have to buy a new regulator:aargh4:!!!
Cheers Frank.