Restore only part of nandroid image
Clockworkmod recovery has an 'Advanced Restore' option that allows you to pick just one of the following partitions:
boot
system
data
cache
sd-ext

If you don't already have it, download ROM Manager from the market and this will help you install the clockworkmod recover.

(I've no idea whether this will solve your problem, but yes you can restore the data partition! ;) )