Dont know if below is bugged, or misleading error message, or both.
Code:
# OK
Blankclip(Length=1,Width=1,height=1,Pixel_type="YV24").PointResize(256,256)
# Resize: source image too small for this resize method. Width=1, Support=1.
Blankclip(Length=1,Width=1,height=1,Pixel_type="YV24").BilinearResize(256,256)
# Resize: source image too small for this resize method. Width=2, Support=2.
Blankclip(Length=1,Width=4,height=4,Pixel_type="YV12").BicubicResize(256,256) # NOTE, YV12, Presumably error for chroma
# Resize: source image too small for this resize method. Width=2, Support=2.
Blankclip(Length=1,Width=2,height=2,Pixel_type="YV24").BicubicResize(256,256) # NOTE, YV24
# Resize: source image too small for this resize method. Width=4, Support=4.
Blankclip(Length=1,Width=4,height=4,Pixel_type="YV24").Lanczos4Resize(256,256)
# Resize: source image too small for this resize method. Width=4, Support=4.
Blankclip(Length=1,Width=4,height=4,Pixel_type="YV24").GaussResize(256,256)
# Resize: source image too small for this resize method. Width=4, Support=4.
Blankclip(Length=1,Width=4,height=4,Pixel_type="YV24").BlackmanResize(256,256)
# Resize: source image too small for this resize method. Width=3, Support=3.
Blankclip(Length=1,Width=3,height=3,Pixel_type="YV24").LanczosResize(256,256)
# Resize: source image too small for this resize method. Width=4, Support=4.
Blankclip(Length=1,Width=4,height=4,Pixel_type="YV24").sincResize(256,256)
# Resize: source image too small for this resize method. Width=2, Support=2.
Blankclip(Length=1,Width=2,height=2,Pixel_type="YV24").Spline16Resize(256,256)
# Resize: source image too small for this resize method. Width=3, Support=3.
Blankclip(Length=1,Width=3,height=3,Pixel_type="YV24").Spline36Resize(256,256)
# Resize: source image too small for this resize method. Width=3, Support=3.
Blankclip(Length=1,Width=3,height=3,Pixel_type="YV24").Spline36Resize(256,256)
Return Last
For eg YV24, width=2, height=2, Says width = 2, Support=2 (when it clearly produces an error message, ie seems not to support 2).
Think its been like this 4E4 (believe it exists as above in avs standard).
EDIT: Presume similar on height, untried.