First time I've seen it. Usually, however, simply restarting the client or rebooting the computer fixes GUI issues (if that is what it is). Also, sometimes odd problems like this are fixed by deleting the Documents / My Games / Final Fantasy XIV folder and running the FFXIV Config program (which you have to do after deleting the folder). I'd try those things and see if that works. If it doesn't fix it, probably a re-install is your next best bet.