transport key commands only work when playback is stopped

I just got a project to mix which was tracked in an older version of Cubase, and since I started working on it Cubase has been behaving strangely. Essentially I have become accustomed to using transport key commands (FF, rew, locators, other markers etc) while playback is happening, but now I have to stop playback first. Is there a preference that would bring back key commands during playback?

Actually, now it looks like I can get it to work normally again by rebooting Cubase. I’m thinking there’s some kind of clash between versions which is embedded in the project files. However, when this happens, any project will behave this way (prior to rebooting C9).