High cpu usage and fast forward not working scince upgrade

[AllesMeins]

I noticed this issue a while ago. Since I've upgraded my system (From Kubuntu 7.04 to 7.10) kaffeine is no longer working as good as it used to. The CPU-Usage during playback is notably higher than before. Every few seconds something flashes on the screen (to short to see clearly what it is) what seems to be a wrong frame.
Playing a video with higher speed isn't possible anymore. When selecting Fast Forward 1x it just gets stuck every few seconds. When playing even faster kaffeine seems to get stuck between to frames going back and forth until skipping to two other frames a few seconds later, sometimes not even (or really slow) reacting on keyboard input. This all worked before the upgrade. Playing the same file in Xine-Player seems to work as well. There it is possible to use Fast Forward with continuing motions (but with CPU-Usage around 90%).
The problem exists with every file i tried so far (various file-types and codecs and some DVDs). Any ideas what might go wrong?