Comment 1 for bug 178823

Heard that this is a problem from GTK+ as Gimp shares the same exact problem, unfortunately.

bug is here http://bugzilla.gnome.org/show_bug.cgi?id=496958

apparently win tab which GTK+ uses for tablets is embroiled in a legal battle, and chances are the Bamboo in particular may not even use the wintab api, which may explain why running gimp with the --no-wintab flag fixes it, but no pressure sensitivity.