Thanks for mentioning this, mtraynham. You're correct in your guess that the image wasn't the right one. I've merged your thread into this one so that you'll get any updates about the fix. At the moment, a fix has been committed to SVN.
This bug has been fixed in the Ext GWT 3.0 Release Candidate. Please upgrade your copy of Ext GWT and try your test case again. While we're confident that we've addressed this issue, please reply if you notice any continued problems after upgrading. Again, thanks for taking the time to report this bug.