Weird transparency problem, please help

[Agathorn]

Ok I don't know how I broke this but i've spent weeks of what little itme I have (I work retail, its xmas season..fill in the blanks ) and I can't fix it.

In the default interface, when you mouse oiver things in your inventory, or hotkeys, etc, there is a tooltip that pops up that tells you what it is and some basic info. On the DEFAULT interface this mouseover tooltip has a background on it so even if it overlays on top of stuff its easy to read. Somehow in MY interface, there is no background. Its completely transparent and therrfore in most cases unreadable. It is driving me nuts and I can't find it ANYWHERE.

Does anyone have any ideas?