Strange Freeze on My MacBook Pro 15.4" 2.0GHZ (A1150 / MA600LL) & No Sound After Boot
Schedule an appointment with the genius bar and bring it to them. At the very least they'll be able to run you the diagnostic tools and tell you what the problem is.

My experience is these sorts of problems usually result in a pretty expensive repair bill, unless you happen to be still covered under apple care support.

Logic board probably has some sort of damage.