Slow Videos

[kosti]

Just recently I've noticed that when I play back videos on my wmplayer, they are very lagged. The sound is in time, but the video is very choppy and slow. Even older video clips I've taken with my camera and which played normally a month ago are slow and choppy now. Even when I use Youtube to look at a video clip, it's also very choppy, while before it played very smooth. Any ideas as to why this is happening all of a sudden??

Thanks
Peter