weird graphical glitch on Start up?

[Goobis]

So I just upgraded my 27" iMac to Mountain Lion last week and now every time I boot up my mac there's this weird rectangle graphic distortion that pops up right as the apple sign appears. After it loads everything is fine and I can use my mac normally. Im just curious what it is. It never happened before Mountain Lion. Any ideas?

Mac specs:

27" iMac
OSX: 10.8.4
Processor: 3.4 GHz intel core i7
memory: 12GB
graphics card: AMD Radeon HD 6970M 2048mb


Cheers

 

[gwang73]

Strange indeed. Try a SMC reset and see if that fixes it.

 

[N4M3Z]

I am seeing a similar issue during boot on my MacBook Pro 2011. Faulty GPU?