Seems this was never answered and I still can't find this option anywhere in XBMC so I'm here with some extra oil for this fire.
Frequently I navigate through XBMC during the playback of a song with a video, switching from the video of that song to the menu takes a few seconds where playback continues so I will miss a part of the song and as some of you may know, that kindof takes the feel out of a song.
Since most of these are 50hz the navigation will not have an impact.
Funny thing is, when you playback a song with just audio and milkdrop is running, XBMC will keep to the framelimit set in Milkdrop. This was 20fps default here so I could clearly notice the difference but it wasn't much of a hassle navigating with such a low refresh rate. (actually it was at 60hz but the interface was limited to ~20fps)
So once again in short, could someone please add a function of keeping the refresh rate of the last played video? Maybe a hotkey for returning to default.
This would make playback of videos much more appealing and isn't that what XBMC is all about?