Of coarse this would happen on a day when the temp drops 40 degrees and decides to rain all day. i rolled the window down this morning on my 2001 SLK230K (105,000 miles) to go through security on my way to work. as soon as i pressed the button and it started to roll down i heard a poping noise that sounded like a rock hitting the window (something broke?) and then the window stopped rolling down at the half way mark and would not go down any more, or go back up. i gave it a minute and the window finally went back up and the regulator seems to be working fine as the window will go up and down with no problem & at normal speed as long as i do not reach the half way point in which it stops. and ideas and advice would be greatly appreciated!