Most likely the driver side windows regulator, if the other windows are working. If you are mechanically inclined and have some tools, you can do the inspection to verify the problem as it is possible it just came off track. Then you can make the repair or replacement as required.
The door trim has to be removed before you can do the inspection.
Discounted price of window regulator from NICO sponsor, IoS is @ $70 per link below
http://www.infinitipartsusa.com/partloc ... atalogid=0