Name check delays coudl happen becuase
1) Very common name
2) You had a criminal issue (DUI etc).
3) You had some issues (not necessarily problmes) while entering US the last time. Like you had DUI, you went for stamping in your home country and got delayed becuase of that. I guess at that time you have enter yess to ever being arrested and also yes to visa ever being rejected. This is separate from I-485 form and is in DS-156 form.
Do I have any justification that above are true, absolutely NO.
Myself
I-140 PD MAr 2001
I-485 RD Dec 2004
Had interview, approval penidng name check.
Received 'no record' FOIPA response.
Send coupel of emails/Faxes to FBI for name check status - NO Reply
Contacted Congressman and they contacted just the INS, so same reply - awaiting FBI response to name check.