I think I found the culprit. I disabled the extension called "Ubuntu Firefox Modifications" and that seems to make the Flash problem go away. Occasionally Flash objects come up as grey boxes (with a "Transferring data from..." message in the status bar) but they load when I refresh the page.
-- Flash plugin fails to display https://bugs.launchpad.net/bugs/322935 You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs