Upgraded from F12 to F13 alpha. The notification area for gmixer is now a red X instead of what it should be.
In the terminal you will see $ gmixer -d W:Failed to load icon Icon 'stock_mic' not present in theme W:Failed to load icon Icon 'stock_line_in' not present in theme W:Failed to load icon Icon 'stock_volume' not present in theme Not sure how these icons are called now, but it shouldn't be too hard to patch gmixer for the new names.
gmixer-1.3-13.fc13 has been submitted as an update for Fedora 13. http://admin.fedoraproject.org/updates/gmixer-1.3-13.fc13
gmixer-1.3-15.fc13 has been pushed to the Fedora 13 testing repository. If problems still persist, please make note of it in this bug report. If you want to test the update, you can install it with su -c 'yum --enablerepo=updates-testing update gmixer'. You can provide feedback for this update here: http://admin.fedoraproject.org/updates/gmixer-1.3-15.fc13
gmixer-1.3-15.fc13 has been pushed to the Fedora 13 stable repository. If problems still persist, please make note of it in this bug report.