This is actually a long-standing bug in the murrine engine, where the text-shadow doesn't get rotated along with the label.
** Package changed: xfce4-panel (Ubuntu) => gtk2-engines-murrine (Ubuntu) -- You received this bug notification because you are a member of Desktop Packages, which is subscribed to gtk2-engines-murrine in Ubuntu. https://bugs.launchpad.net/bugs/1299516 Title: Font rendering in some plugins is broken when the panel is vertical. Status in “gtk2-engines-murrine” package in Ubuntu: Confirmed Bug description: There are font rendering issues in *some* plugins when the panel is set vertically. The black outline for the font is correctly displayed horizontally. The white core of the font is displayed vertically. Known faulting plugins : "System Load Monitor" and "CPU Frequency Monitor". Known working plugin : "Sensor plugin". Release info : Description: Ubuntu Trusty Tahr (development branch) Release: 14.04 ProblemType: Bug DistroRelease: Ubuntu 14.04 Package: xfce4-panel 4.11.0-0ubuntu1 ProcVersionSignature: Ubuntu 3.13.0-20.42-generic 3.13.7 Uname: Linux 3.13.0-20-generic x86_64 ApportVersion: 2.13.3-0ubuntu1 Architecture: amd64 CurrentDesktop: XFCE Date: Sat Mar 29 17:09:35 2014 InstallationDate: Installed on 2014-02-09 (48 days ago) InstallationMedia: Xubuntu 14.04 LTS "Trusty Tahr" - Alpha amd64 (20140209) SourcePackage: xfce4-panel UpgradeStatus: No upgrade log present (probably fresh install) To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/gtk2-engines-murrine/+bug/1299516/+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