i've done that more times than i can count...possibly a version of a filter that's not optimized for my system? look at my script and see if you see anything that could be doing it...
LoadPlugin("D:\VCD Shit\Movie Stacker\Filters\Mpeg2Dec.dll")
LoadPlugin("D:\VCD Shit\Movie Stacker\Filters\GripFit_preview.dll")
LoadPlugin("D:\VCD Shit\Movie Stacker\Filters\Unfilter.dll")
LoadPlugin("D:\VCD Shit\Movie Stacker\Filters\LegalClip.dll")
LoadPlugin("D:\VCD Shit\Movie Stacker\Filters\Sampler.dll")
LoadPlugin("D:\VCD Shit\Movie Stacker\Filters\STMedianFilter.dll")
AviSource("knockaround guys.avi",false)
ConverttoYUY2
LegalClip()
GripCrop(704, 480, overscan=2, source_anamorphic=false)
GripSize(resizer="LanczosResize")
STMedianFilter(10, 50, 0, 0, 10, 50)
unfilter(50,50)
temporalsmoother(1,2)
mergechroma(blur(1.5

)
mergeluma(blur(0.2))
GripBorders()
LegalClip()
#Sampler(length=24)