My phone has
1) the bootloader unlocked
2) usb debug mode enabled
My PC has
1) the Android SDK installed to use adb and fastbook
To regain root following an OTA update
1) Download "ClockworkMod Touch" recovery from http://www.clockworkmod.com/rommanager to C:\sekhonp\installation\
2) Download su from http://download.clockworkmod.com/test/su.zip to C:\sekhonp\installation\
3) Plugin phone into usb port and ensure usb debug mode is on
4) cd "C:\Program Files (x86)\Android\android-sdk\platform-tools"
5) adb push C:\sekhonp\installation\su.zip /sdcard/
6) reboot phone into bootloader menu, but don't switch to recovery mode
7) ..\tools\fastboot flash recovery C:\sekhonp\installation\recovery-clockwork-touch-5.8.0.2-crespo.img (replace path with downloaded image)
8) Switch into recovery mode and install /sdcard/su.zip
9) Reboot
10) Open Root Explorer, change to /etc, mount r/w, delete /etc/install-recovery.sh, mount r/o
11) Open Rom Manager and flash "ClockworkMod Touch" recovery (as it would have been deleted by /etc/install-recovery.sh in previous reboot)