A prior immigration violation such as the expiration of a visa is not grounds for denial of the N-400. It is common for USCIS to delay a decision. However, if you are concerned, I recommend you contact a local San Diego immigration attorney who can follow up with your application on your behalf.
I agree with my colleagues.
(213) 394-4554 x0 Mr. Shusterman is a former INS Trial Attorney (1976-82) with over 35 years of immigration experience. His response to your question is general in nature, as not all the facts are known to him. You should retain an attorney experienced in immigration law to review all the facts in your case in order to receive advice specific to your case. Mr. Shusterman's statement above does not create an attorney/client relationship.