Attempting to boot into diagnostic, i get a gray screen

I have a mid 2010 Macbook pro 13".

The computer froze on me for some reason while on the screen saver. I reset the computer and it worked fine.. Maybe slightly slower than I am used to, but I might be wrong. The computer was also very hot on the bottom left side. At that point I decided to boot into diagnosis to check the systems. I booted while holding the D key, and it took me to a gray screen and from there, nowhere...
Tried the C key, and it did the same...

Once in OS x lion, I went to about this mac, then more info, then system report. Under Diagnostics, it shows passed...

I am really in loss to understand what is going on here...

Anyone has any insights?

Thanks
Gilad