It will be the window regulator, Probably a snapped wire. Sounds like the motor is fine Had this on my freelander , and by looking at the pictures of parts on ebay , they look pretty similiar.
The first time this happened , my local garage fixed , but releaved me of £150.
Next time it happened , I did it myself , not a difficult job , justa bit fiddly.
The worst part is getting the door card off , just finding where all the screws are.
But after that it was a simple job of unscrewing the window glass from the clamps (remember to tape the window glass securely to the door frame , don't want glass to fall and break )
The unscrewing the old regulator , and getting it out of the door frame (lots of cut fingers on the freelander) , then putting ther new reg in , connecting the motor , remounting the glass , and putting back the door card.
Just be careful you don't get the wires snagged when putting in the new reg.
As I say, I did this on a freelander not my Alfa , but I would imagine the jobs pretty similar.
Took my about 90 minutes all in , (with 10 minutes of swearing ) , I'm not mechanically minded , but after looking at lots of youtube videos I tackled it myself & it wasn't that difficult -and I saved over £100 notes (and with a 3.2 159 - thats a tank of fuel.
Just one point , If the window is currently closed, don't use it until fixed, I did this and found that the window stopped halfway down and the broken wire snagged internally , and I couldn't get the window back up , not good in the rain.
If you have the time , give it a shot , you will save money and have a stamp on your 'man card'