x264vfw on notebook with "slow" preset casued frames "jump" back and forth

[xingyanchao]

I wasted a lot of time on this issue:
while compressing the 720*576 video with x264vfw (set to 300kbps) on my notebook (TravelMate 6292), it seemed that the frames often jumped back and forth -- if you just moved from left to right, the result would be that you ofen moved back to the left then to the right.
At first I doubted there was some frame sequence problem, but checked with the mkvinfo.exe, everything appeared normal.
Then I use the x264.exe to compress the raw video data, the result was fine, BUT the time it took was longer than the video clip.
So I guess the real reason should be that my notebook could not work fast enough, then the buffer for output was not updated when we need to output a frame.
Obviously, the visual result is annoying, how could I solve this problem, say -- keep the last frame if the new frame is not ready yet?
Thanks for help!

Sam