After a large amount of testing and finally correlating logs, I determined this to be caused by installing version 1.3.10a of the flashblock extension though apt. I use amd64, kubuntu intrepid, Kde 4.1 (and 4.2), nvidia drivers, and QtCurve. I think the last two looked like they may have been related, but probably aren't.
1.3.10a in the repositories is too old; I switched to version 1.5.7.1 from addons.mozilla.org and my problems have finally resolved.
Lesson: don't install Firefox extensions from apt.
After a large amount of testing and finally correlating logs, I determined this to be caused by installing version 1.3.10a of the flashblock extension though apt. I use amd64, kubuntu intrepid, Kde 4.1 (and 4.2), nvidia drivers, and QtCurve. I think the last two looked like they may have been related, but probably aren't.
1.3.10a in the repositories is too old; I switched to version 1.5.7.1 from addons.mozilla.org and my problems have finally resolved.
Lesson: don't install Firefox extensions from apt.