ogm: how come jump to keyframe when switch to fullscreen?

[PeterTheMaster]

if this is an ogm problem please move to new a/v.

i made some .ogm file (containing a divx502 video and an ogg audio stream)
i use wmp 6.4. everytime i switch to full screen mode, the movie jumps to the next keyframe, so if i switch fullscreen, small, fullscreen, small ... its like fast forwarding. on my other 2 computers this doesnt happen, so what might be the cause? hardware accelleration is set to maximum.
this also does not happen with the mute divx502 avi file.

[QuoVadis]

On the properties page of the OGG codec is a checkbox to perform a faster search by jumping to keyframes when searching. Ucheck this and the problem should be solved.