I'm on nighties 39 and some of my CM settings and phone settings don't save. It reverts back after I leave the screen. Anyone else having this issue? Or is this a feature? LOL
Not sure if this will help, but I was finding that my brightness would always reset after turning the screen off/back on. I realized that the CM7 Notification Bar Widget was overriding whatever I had set in settings - ex I had it set to 50%, turned screen on it would be at 100% because that's what the widget setting was. Once I changed it in the widget it remained at what I wanted.
I know this is a cpl days old, but I have had the same problem since nightly #36. I figured out that the system was not remounting itself after making a change. I tried a little different install this morning. I manually mounted the system while installing the nightly. So far,so good. Also, wiping dalvik this time too. Hope that helps you as well.
I am also having this issue and I tried installing the latest nightly after manually mounting /system in recovery and wiping dalvik cache.... I have SBF'd several times and this issue always comes back after the first or second reboot in cyanogenmod. This must not be a very widespread issue because this is one of only 2 threads I have seen about it.