This happens only if you are switching the fader banks upwards, lets say from 1-8 to 9-16 from the moment the curser leaves the first time the right end of the edit window, right? And when you activate "scrolling during playback" the edit windows flickers between your actual playback point and the start of the song. And from that moment your keyboard inputs get ignored as the curser blinks fast and stays at the start (left side). - If this is what you experience the it is the same bug I was referring to some weeks ago.
See my original post about it:
Strange behaviour
I had this bug from the very start I installed 7.3.1cs2 and it didn't disappear on cs3 although DTS stated that they were about to fix it. See my second post about it:
Second post
From my view it seems as if the left curser button is pressed constantly. As I described I did a workaround in creating 8 tracks more than I actually need, so I switch the fader banke twice upwards and immediately once downwards so I can see the tracs I want. Maybe this helps you out until they bring out hte next cs.