| | easier in-between step
My Curve was hardly scrolling down at all, completely unusable. I was a bit worried about the full procedure outlined here, and i did a halfway job that fully restored my Curve. I took the ball assembly out and gave it a good cleaning with rubbing alchohol and Q-Tip swab, along with strong puffs of air (from the mouth).
Takng the ball assembly out of the handset lets the ball move more during cleaning, and allows blowing air through it.
Note, there are low spots under the silver ring at 2 o'clock and 10 o'clock, which appear to be best places to pry with a small screwdriver.
I did not take apart the ball assembly, and i'm glad it wasn't needed!