Unfortunalty, it is not off track, most likely the Power Window Regulator has broken and no longer supports the window. This isn't a difficult repair, once you get over removing the door trim panel.
-Rip
Lead Technician
A.S.E. Master Technician, Advanced Level, Smog - European, Domestic, & Asian -- Car Category Mentor
Let me see what I can come up with, and i'll post it shortly. I may not have step by step directions, since door panel removal is not offered in our reference, but in any case i'll be able to guide you thru the repair if you need. Be back in a few...
Alright, here's some pics...i'm going to try and locate some on the removal of the door panel tonight and post them - but don't hold me to it just yet.
Schematic of the door, with panel removed, weather sheild removed, and regulator exposed.
This is how the regulator looks once you've removed it.
Thanks for being patient. Unfortunalty, I could not find any good illustrations, but I did locate written literature on the removal process. I've posted it below...let me know if you need any further help.
Door Trim Panel '99 528 - Rear