Re: Immigration/Citizenship
It has nothing to do with INS (or USCIS as its called now). The background check is stuck at FBI, and this is increasingly a common problem. I am guessing your husband's name is not very unique, so it could be popped up in some random list; hence the delay.
Technically your husband can approach FBI directly, and ask them to run his background check and provide him a report. By law they are required to turn it around in fairly short order. This still won't solve the problem that FBI is sitting on its lazy arse and not providing clearance to USCIS.
Once you have gone past 2.5 years of wait, you should consider filing a law suit against USCIS and FBI for not processing your case. This may be your best option at that time. I know several people who got stuck at greencard as well as citizenship process for exactly this same issue. After you file the law suit, chances are that USCIS and FBI will settle with you and process the case. Consult and retain a good immigration lawyer before proceeding. Its an investment worth the money.