I don't know about if there is a new rule, but even before you had to wait 90 days even as an asylee. The same thing happened to me, and when I went to the local office, they send me back saying I have to wait 90 days. I had the printout from their web site, and I showed them it said 30 days. The lady screamed at me if front of everybody and asked me if I knew her job more than she does. She was so rude, she even made me cry. It was right after Sept 11 and their attitude towards foreigners was really bad.
Anyway, even under their old rules, you have to wait 90 days. Anyway, check again or try to make an infopass as well to make sure you have the right answer! Good luck!
PS. Make sure you take your receipt (the one you got from USCIS). You have to prove that 90 days have passed.