yep, like others posting here, I wouldn't put much credo into online updates. it's one of their least efficient products. i recieved my IL recently, though the online status continues to display a "We received your N400 application..." since over a year ago.
If I were you, I'd perhaps be more interested in the Online Tracker someone from your city maintains. At the same time, wouldn't be a bad idea to call the USCIS number someone mentioned earlier to obtain an update.
~my 2 cents worth.....