I can't replicate your issue. If i open the script in Virtualdub (with either 2.6.0, 2.6.1a1 (AviSynth_20160517_VC2008Exp SSE2.exe) or latest csv) i get no errors.
I got an error though if i convert the solution to msvc2010, compile a debug build and run the script
Code:
ColorBars(width=720, height=480, pixel_type="RGB32")
ConvertToY8() # crashes on this line
ConvertToRGB32()
If i click on negeren (= ignore) the script loads fine. If i compile a release build the script runs also fine