Can Someone tell me why firefox is half invisable?

[CrayonMuncher]

half of my firefox has gone invisable the home page will load up (google) work but all the menus, exit buttons and pretty much anything that is'nt the webpage is invisable with just plain text and i am unable to click on anything so i have to exit through task manager, anyone know why, probably a re-install will fix it but i really want to know why

 

[bkribbs]

have you tried reinstalling it yet?

 

[CrayonMuncher]

yeah that fixed it but i just wonder why it happened seems like a very strange error and i cant find anyone else on the web with the same issue