installed do 9540 and turned off preferences, miscellaneous options, check for updates, rebooted and check for updates was turned ON again.
have repeated check of behaviour on two separate machines, same thing happened.
I don't like it, too, but I think this is a feature not a bug since this happens in all Do 9 Versions.
If you're talking about the Miscellaneous->Options->Check for program updates automatically option - then I don't see why you would call this a "feature".
It's not "supposed" to turn back on if you turn it off. Something on your "system" (permissions, etc) is most likely causing the change you're making not to be saved. If you turn the update check option off, then "exit" Opus (actually right click the system tray icon and click Exit) and restart Opus without rebooting - is the option still "off"?
In this case it will stay off, but not after installing a new version.
Feature meant: It's turned on automatically after installing update or after fresh install AND importing settings.