It appears that the issue is caused by a color depth issue.
For me, when running gnome-do from the console I get:
"Gdk-WARNING **: Attempt to draw a drawable with depth 24 to a drawable with depth 32"
Using xwininfo, I can verify that the preferences dialog is the only window on my desktop thats running in depth of 24 (even the dock is running in depth 32).
It appears that the issue is caused by a color depth issue.
For me, when running gnome-do from the console I get:
"Gdk-WARNING **: Attempt to draw a drawable with depth 24 to a drawable with depth 32"
Using xwininfo, I can verify that the preferences dialog is the only window on my desktop thats running in depth of 24 (even the dock is running in depth 32).