I had already reported this in another thread, but wanted to make a thread of its own so Neil could find it.
Bug: when switching from WB skin to Aero and then back to WB, a lot of the fonts get reset to Tahoma (the statusbar/addressbar/rightclick menus/bookmark dropdown menus in Firefox). The tooltip on the taskbar clock also becomes Tahoma as well as menu bar items on things like mIRC and notepad.
So far the only way I've found to fix it is to logoff/reboot, which is rather annoying.