Not sure about dbc but dbpro usage is slight different.
It is GET IMAGE img,X1,Y1,X2,Y2,FLAG
where;
X1 = left
Y1 = top
X2 = right (but should be one more that you think)
Y2 = bottom (but should be one more than you think)
FLAG = set to 1 to grab the image pixel perfect. If you exclude the flag or use 0 it will get the image blurred, ie it will grab it for use in 3D models with mipmaps.
So using GET IMAGE 0,0,63,63,1 is what you would expect to grab a 64 by 64 pixel image but actually grabs a 63 by 63 image. So you must use 0,0,64,64,1
[EDIT] Edited to fix my stupid typos. Thanks Scraggle!
Boo!