Can't enter recovery mode on nexus s

[d_pang]

I just rooted my nexus s and while trying to get into recovery mode to install cyanogenmod7 nothing happens after I click on recovery mode. Instead I am left at the google screen with a unlock icon at the bottom of the screen. I have found the only way to exit this screen is to do a battery repull and reboot my phone. I have flashed my clockwork with rom manager. I don't know what's wrong. Any help would be appreciated thanks.