Thunderbolt Monitor Trouble

Okay, so I have MacBook Pro, it has lion, and just last week I visited the apple store to get the power... part... replaced. When I got my laptop in August 2011, I got a larger monitor (from apple) to run off of my laptop through the thunderbolt cable. It's had a few issues here and there like when I'm running it, videos don't buffer very well. But in the last week, at least once per day I have been getting a "You need to restart your computer, hold down the power button" message. Yesterday it happened 3 times. I don't understand, since the monitor was bought with the laptop for the singular reason to be run off of it.

Might I have accidentally downloaded something that made it not work? How do I fix it?

Your post was moved here to the correct forum. It did not belong in iOS and Apps..... as that forum is for mobile devices such as the iPhone, iPad, etc.

EDIT: Please do not cross post. (posting the same thread to more than one forum) Your other post has been removed.