I had the problem but I fixed it. This is what I did:
Go into the FS app Settings>facebook> make sure both sync live feed and sync contact is checked
Now go into twitter and do the exact same thing except it will says sync peep and sync friend, make sure both are checked.
Now from the home screen menu>settings>accounts & sync> and make sure the auto sync is checked.
Also, make sure both facebook and twitter are set to update at the same time, like every hour.
I had one of those boxes unchecked and now mine updates every hour.