Can't open any programs

My Macbook Pro has been acting pretty strange lately... It started being very laggy and freezing up so I ran Disk Utility and found there were some errors when I verified the disk. So I popped in the install disc and repaired the errors. Yadda yadda.

My computer is running FINE now but every time I try to open a program, ANY program, the computer freezes and I get "the application has quit unexpectedly."

Running Snow Leopard btw...

It sounds very much like your hard drive is dying. If you haven't already done so, start making backups using Time Machine or cloning software. And then be prepared to swap out that hard drive with a new one.

That's the scary thing - my hard drive DID die, and I had it replaced. Now 4 months later the replacement is making chirping and scratching noises.

Take it back where you had the drive changed out. If it was Apple that did the replacement, it should still be under warranty. BTW, nothing unusual about having a new drive fail within four months. I've been there and done that several times.