I must begin by telling you that I have searched for an answer to this since I updated to 2.1 and have tried all kinds of posted "solutions". After going to sprint's 2.1, I was unable to get any facebook contact photos in my "people" app. I also experienced same problem with many diff rooted 2.1 roms.
NOW, this may sound strange but the only thing that FIXED this is I got rid of my high-school and college details in facebook profile while on my home computer. All of a sudden, everything works using "facebook for htc sense" on the phone!
Give it a try if nothing has worked & pass info along if you get results.
I have not tried adding back the school info in profile, kind of afraid.