Cyrix MediaGX, 32Mb RAM, running Pinstripe X,
GNOME and Window Maker.

When I move windows around with Window Maker and
'opaque' window-moving (ie, the whole window follows
the mouse immediately), I get thin vertical lines appearing
down the window. When I do this with 'box'  (or something:
only the borders moving when moving the mouse), it 
doesn't happen. I can get rid of the vertical lines by
shading and unshading the window (they remain on the
titlebar though). 

Suggestion is that this is a "miscompile" or an "off-by-one"
error. I hope you know what that means. I don't, I got it from
someone else...