In 12.04, the screen never went to sleep while watching videos in XBMC. However after upgrading to 12.10 and changing no settings, it does.
Is there any way I can prevent the screen automatically turning off while playing a video in XBMC, without actually disabling the screen from turning off at other times?
Ideally, is there a XBMC specific setting for this? Was this a feature of XBMC that is now somehow broken in 12.10 or has this changed due to some other non-XBMC change within Ubuntu?
This seems to be a bug in the XBMC package for ubuntu
I'm not sure what version you have installed, but the version from the PPA* doesn't seem to have it on my system. This can be because I have different settings in ubuntu of course, so your milleage may vary.
If you don't, you can try to use XBMC as a session (on your login-screen, press the ubuntu logo next to your name and select XBMC. You won't get unity, but just fullscreen XMBC). The settings for unity will not be there, so you might luck out on not having a screensaver. (If you have auto-login set, you need to press logout to get the login screen)