Hope this isn't considered a hijack but I have the same issue.
I have a rooted Aria and have stable/gingerbread/update-cm-7.1.0-Liberty-signed.zip on my phone. It started to reboot after I took some updates from the Android Marketplace. I don't know which update is causing it, if any.
I put on RC/update-cm-7.2.0-RC1-liberty-signed.zip and the rebooting went away for about a week and now has started up again. There may be some automatic updates that I have set up and I believe this is the major problem.
Is there a program out there that I can us to determine the newest updates, chronically?