I had a boot loop today as well when I did the 3.0.5 update. Luckily I could easily enter webOS recovery mode immediately after it rebooted, I doctored, which of course broke Android, so I reflashed CM9 0.6, CWM and moboot, expecting to have to do a restore of my last backup (which I made and copied to my computer prior to doing the webOS update.
Luckily, I didn't even need to restore and all my Android settings were just as I left them, and webOS is on 3.0.5 (I'm syncing all my webOS apps now...which takes way too darn long). Frankly I hope HP leaves 3.0.5 as the last version so I don't need to bother with this again. Took forever.