For some reason when I test this avs script

AviSource("E:\Completed\movie.avi", false)
BlindPP(cpu=4)
Blockbuster(method="noise",detail_min=1,detail_max =6,variance=0.2,seed=5623)
Convolution3D(1, 6, 12, 6, 8, 2.8, 0)
GripCrop(352, 288, overscan=1, source_anamorphic=false)
GripSize(resizer="LanczosResize")
Undot()
TemporalSoften(2,7,7,3,2)
DCTFilter(1,1,1,1,1,1,0.5,0)
GripBorders()
Textsub("E:\Completed\movie.srt")

I get a scene from the movie flash on the screen for 1 second, and the edge is rather blurry like there is a line of frosted glass.If I put it to 352,240 it doens't happen but my movie looks slightly squashed. How do I edit my script so that won't happen?

Is your source pal or ntsc ?

25fps so PAL

And this problem appears on only ONE SCENE ?

No real need to change a script for that. I'm sure the problems is in the source.

Note: you shouldn't modif the scripts from the original one without knowing what you are doing. The blockbuster line you have isn't correct.