Whoa, that's wild. Everything's shifted but black and white!
I have no idea what could be causing that.
In the off chance that it might help, I've just uploaded the PNG engine
from my copy of the extension to alt.binaries.freeware. It's called
canvas2png.dll and it goes in
C:\Documents and Settings\USER_NAME\Application Data\Mozilla\Firefox
\Profiles\PROFILE_HANDLE\extensions\{LONGASS_CLASS_ID}\platform
\WINNT_x86-msvc\components
Maybe swapping it for your's will fix it.
Thank you for your effort Charlie. I grabbed your version, noticed it was
version 0.9.0.0, same as mine and exactly the same size also. Replaced
mine with it anyway. Made no difference. Rebooted. Still no difference.
I'll try to contact the author. For now, I'll do the double job (save the
png, open the png in Firefox and save a png from that again), not very
convenient, but it works.
Thanks again for your effort.