My encode result is a green messed up video

[Selur]

Nope it's not the x264 call itself.
The encoding call:

"C:/PROGRA~1/Hybrid\ffmpeg.exe" -y -loglevel fatal -noautorotate -nostdin -threads 8 -i "C:\Users\User\Desktop\hxhf\script.avs" -an -sn -vf  scale=out_range=tv -pix_fmt yuv420p -vsync 0  -f rawvideo - | "C:/PROGRA~1/Hybrid\x264.exe" --preset superfast --pass 1 --bitrate 1500 --profile high --level 4.1 --direct auto --sync-lookahead 12 --qcomp 0.5 --rc-lookahead 40 --aq-mode 0 --thread-input --sar 1:1 --non-deterministic --stats "C:\Users\User\AppData\Local\Temp\final_18_57_44_0910_01.stats" --demuxer raw --input-res 1280x720 --input-csp i420 --input-depth 8 --fps 24000/1001 --output NUL -

looks fine to me.

Okay, something is 'off'.
The location of you ffmpeg is wrong. (tools are sorted into 32bit and 64bit folder since 2014.07.03.1)
-> Deinstall Hybrid completely (with all settings) and reinstall the dev verison, then try again.

Cu Selur