Hello Guys,
Google has broadcast another OTA for android 2.2 for AT&T and T-Mobile nexus one. It's Build FRF91. You can check for OTA or manually install it on device.
To update manually from FRF85B to FRF91 follow the link.
http://android.clients.google.com/packages/passion/signed-passion-FRF91-from-FRF85B.db99fdf1.zip
if you don't know how to manually install it. follow the steps
Download the official Android 2.2 firmware for the Nexus One.Copy the file to your microSD card and name it update.zip (newb warning: not update.zip.zip)Power off your phone.Hold down the VOLUME DOWN button and power it back on.The phone will now search for files like PB00IMG.zip, etc. This is normal. Scroll down to recovery and press the POWER button.When you see the ?/!\? symbol, press the POWER button and the Volume Up button at the same time. You should be presented with a menu and one of the options should be ?Apply sdcard:update.zip?.Use the trackball to navigate to ?apply sdcard:update.zip? and select it.When you see ?Install from sdcard complete?, select ?reboot system now?.