If luna is crashing as soon as it starts after using WebOS Doctor, one reason could be a missing Homebrew App that used to be in the Quick Launch Bar.
Reinstall the missing Application. Crashes can be supressed by connecting to computer and not choosing between 'just charging' and 'USB-Disk'. Then you'll be able to activate the Developer Mode to reinstall.
Phone: HP Veer (O2) - Webos 2.1.1
After using the Webos Doctor, my Veer started to reboot as soon as I entered the sim key. I knew that it had to be some part of a patch i had installed that wasn't removed. I spend two days trying to find out what traces might have been left. And it took those two days to notice that the phone was stable while it was connected to my computer with the USB selection active. Five minutes later i was sure it was the Quick Launch Bar. And 10 minutes later I remembered that i put the Agenda(as app) on the bar.
I'm posting this as I didn't find any solution in the Forums but stumbled across one shortly before sending my phone back. I actually already believed it was a hardware defect at that point.
If there is a better place for the thread/information feel free to move it, copy it or whatever. (btw I didn't post it to HP yet because i'm not sure this is hps problem)