I had this problem as well and managed to fix it by uninstalling the 'unclutter' package. This program hides your mouse pointer after a couple seconds of it not moving, which apparently also triggered the Firefox tooltip to disappear. I uninstalled this package, logged out and back in, and now my Firefox tooltips work again.
-- You received this bug notification because you are a member of Desktop Packages, which is subscribed to firefox in Ubuntu. https://bugs.launchpad.net/bugs/782049 Title: firefox tooltip timeout after ~2sec Status in “firefox” package in Ubuntu: Confirmed Bug description: Binary package hint: firefox When you want to read a tooltip on a webpage (the "title" tag in an image) like on xkcd it is impossible because the tooltip disapears after ~2sec ProblemType: Bug DistroRelease: Ubuntu 11.04 Package: firefox 4.0.1+build1+nobinonly-0ubuntu0.11.04.2 ProcVersionSignature: Ubuntu 2.6.38-9.43-generic 2.6.38.4 Uname: Linux 2.6.38-9-generic x86_64 Architecture: amd64 Date: Fri May 13 09:42:23 2011 FirefoxPackages: firefox 4.0.1+build1+nobinonly-0ubuntu0.11.04.2 flashplugin-installer 10.2.159.1ubuntu1 adobe-flashplugin N/A icedtea-plugin N/A InstallationMedia: Ubuntu 11.04 "Natty Narwhal" - Beta amd64 (20110413) ProcEnviron: LANGUAGE=en_US:en PATH=(custom, user) LANG=en_US.UTF-8 SHELL=/bin/bash SourcePackage: firefox UpgradeStatus: No upgrade log present (probably fresh install) To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/firefox/+bug/782049/+subscriptions -- Mailing list: https://launchpad.net/~desktop-packages Post to : desktop-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~desktop-packages More help : https://help.launchpad.net/ListHelp
