I have the same problem on my clk-it doesn't raise once unlocked, and it slaps down. I was told the cables went bad and its an expensive fix. So far I have decided to live with it.

__________________
87 300e (white/black; amg body kit)
88 300ce (red/cream; amg body kit)
93 300ce cabrio (white/blue/blue top)
93 300ce cabrio (black/grey/black top)
98 ml 320 (totaled @ 137,000 miles)
99 clk320 (black/grey/black top)