Care to share which OS you are using?
It would help us to know which MBP model you have, which OS & version you're using, how much RAM, etc. You can have this info displayed on the bottom of every post by completing your system profile and filling in the information asked for.
This will help in providing you with the proper and/or correct solutions.
See Article: http://support.apple.com/kb/TS2377 MacBook Pro: Distorted video or no video issues
These computers were manufactured between approximately May 2007 and September 2008 to determine if it applies to your model MBP.
I guess my OS is the one before the latest
The latest OS is Mountain Lion (10.8.3). You confirmed in your original post that you are using Lion (10.7.x). "I was trying to updating my Lion system."
Max out your RAM