Very Odd Behavior in 1.5.1 Behavior playground.. a box?

Hey all,

So I've been playing around with 113 but installed 151 to check it out. On the behavior playground in the editor there's the normal stuff but when I run the game, in the upper middle of the box, it looks as though theres some gui control or button or box or something. It highlights when I mouse over it and it's really odd. I tried 2 computers and they both have the same thing. Looking in the editor though I don't see anything apparent that is causing this. I didn't open up the scripts and start digging yet and I tried a rudimentary search on the forums. So has anyone seen this or am I going crazy?

Thanks!

-Will