I've tried every sensor that MBM lists and it doesn't seem to make a difference. When it doesn't want to work it just doesn't work. Could the BIOS revision have anything to do with it? I'm trying to narrow down from the things that I've done and a BIOS update is one of them, although I'm not sure if the two things coincided.
I downloaded the new version of MBM5 and did and update to my existing installation and had the same issue. I then had the thought that it might be better to do a full install than an update. (After seeing first hand how much trouble creating installs can be) So I uninstalled my existing installation of MBM5 and tried installing a fresh copy. Once I rebooted I gave it a try (a few times) and kept getting a message that it couldn't install the new MBMIO driver. The fix for this is to log in as the local admin. Even though I was logged in as a user that had administrator rights, apparently this was different than being logged in as the "real" machine admin.
Bottom line... I'm now getting temps again consistently.