Could be, but as far as I know battery only supports real-time clock and has nothing to do with keeping settings.
I'm facing the same problem in my DS 7208 HGHI-SH DVR. I'm unable to save any changes, it all reverts back to default on re-boot. Can't change the OSD settings, Camera view settings , nothing.
I'm even unable to update my firmware which is on 3.1.7. Have no idea what to do now.
Will try out changing the batteries inside the DVR ( if it's there )