since, our overlays still show incorrectly on the Tardis machines, I decided to do a little bit of research. This is a post from the OGRE forums, that describes a similar problem:
http://www.ogre3d.org/phpBB2/viewtopic. ... ht=overlay
Anyway, I admit not understanding too much, but apparently the problem was solved:
I think he means mip maps. Could there be a similar reason for the crappy overlays in Orxonox?The problems disappeared once I disabled min maps for the png texture (leaving it 1x1 size).