Comment 2 for bug 847940

More discussion here http://bugs.freepascal.org/view.php?id=19266, eg

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The overlay scroll bars are the culprit. Ubuntu is maintaining a blacklist of applications that don't work with these new, IMO ugly, scroll bars. On an almost daily basis apps are added to the blacklist. Examples: https://bugs.launchpad.net/ubuntu/natty/+source/overlay-scrollbar/+bug/770304, [^] https://launchpad.net/ubuntu/natty/+source/overlay-scrollbar/+changelog, [^] etc. The blacklist is apparently not a simple file that can be edited.

To disable the overlay scroll bars for all applications(from terminal):
sudo su
echo "export LIBOVERLAY_SCROLLBAR=0" >> /etc/X11/Xsession.d/80overlayscrollbars

Log out and you are back to the old scroll bars.

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This is ubuntu unity + liboverlay problem not fixable by us. export LIBOVERLAY_SCROLLBAR=0 is solution.