Okay I found this same game.con error:

http://www.dcemu.co.uk/vbulletin/showthread.php?t=80584

Here they claim that's harmless to the game however I don't get this warning when I start the game and you can I should be using the exact same game data and .deb files so.....

Please remove your duke3d directory but DON'T uninstall the .deb file.

rm -Rf /media/mmc1/share/duke3d

Now replace it with a copy of mine:

http://www.besh.com/~chad/duke3d.tgz

Move the *.tgz file to /media/mmc1/share
then execute:

tar -zxvf duke3d.tgz

Now try and run the game.