urgent help! 485/name check

Here is what happened to me. Filed 485 in Dec'2004, FP in Apr'05, then LUD indicated that they got FP results and started to process my application.

Then in Jul, I moved, so called and changed address. My hu*****and received a letter saying address has been updated, a few days later, I received a mail saying that address is updated, and my case will be delayed because they are performing security check.

Why/how could this happen? anyone have similar experience? thanks!