Recently I got my folks a Nexus 7 3G and I've been using it too with a Multi-User setup with a face lock. While trying to pimp out the N7... I've had a few bootloops. I soon realized that the Wugs toolkit can get you out. That being said... today I bootlooped my Evo V. I decided to try something on a whim. The same Wugs Toolkit for the N7 kicked me back to recovery.
I assume that this trick works with all Androids but I can't say for sure. When your phone is stuck in a bootloop... plug in the USB and fire up the Wugs toolkit. Click on the grey "Launch" button. On the pop up window click the button "Reboot Recovery". Now do whatever you need to in recovery mode to fix your problem.