I asked for some advice in December 2003 under the subject "Power Window with a mind of its own wants to open by itself - 89 900 Aero/SPG" and received lots of useful advice from exorcism to cleaning the switch. I cleaned the switch (and swore at it a few times) and the problem went away for a while. A few months later we went into cooler weather when the window demon seems to hibernate and things were quiet.
Now that we're getting into spring and we're getting a few warm days, the demon has awoken. I cleaned the switch again and it made no difference. I phoned my service place and was advised that I could get a new or working second hand switch. Feeling safe, I decided to modify the switch to disable the auto-down feature. When I took the switches apart, I'd noticed that the switch with the auto-down feature had an extra leaf-like spring thing. So I cut it off. That seems to have done the job. OK, the window did wind down as soon as I turned the ignition on after installing the modified switch. But I think that had something to do with the auto-down mechanism still being "on". That was two days ago. The demon has been sleeping since then.