I have an AVIC N3 and did the same thing. It wouldn't let me search no matter what condition the car was in (parking brake, stopped, etc). Everything else worked (radio, ipod). I thought it might have been a bad burn, but I tried it again with two new higher quality (ie more expensive) dl dvds and produced the same results. So, I ended up flashing it back to the original 60m disk. Everything works as it did before.
If it helps, I bypassed using the switch on the brain.