Real-Time Peak Overload

My Real-Time Peak started to overload in a project that I’m working without I do anything, and I can’t imagine why!

If I open a new project, the Real-Time Peak overloads very easily.

What it can be?

I use a Mac Mountain Lion 10.8, 4GB of RAM, i7 2.2GHz. It was working fine but now I just can’t work anymore!

Please, anybody help me?

Thanks for the attention!