I had the same error running ADT on Ubuntu 13.04 with Gnome Shell 3.8.
I found this relevant bug report: https://bugs.eclipse.org/bugs/show_bug.cgi?id=404776
And a workaround as posted in the bug report:
Add
-Dorg.eclipse.swt.browser.DefaultType=mozilla
to your eclipse.ini
It worked for me, I hope it solves the problem for you as well.