Macbook Pro restarts or freezes after Lion upgrade!

Question

My 2007 Macbook Pro restarts (without warning-it's like losing power and get it back immediately) or freezes EVERYTIME when certain key combinations are used, e.g -b (minus then letter b, not at the same time), copy a sentence long and Ctrl-v, and some others that i am not even aware of.
This happens only after i updated to Lion! First, i thought it is because of the OS, but it crashed even in single mode with those key pressed. So, i used Apple Hardware Test, but it freezes during the test, every time 
I tried resetting PRAM,SMC already. This is very weird and I have googled for all day long, hoping to find an answer for this problem but got no luck at all!
As my last attempt today, i backup data, format the hard drive and install Tiger. However, the problem persists. I am Vietnam, so take it to an apple store is not an option as we dont have any here!
Do you guys have any idea? This is driving crazy! 4 clients are chasing me :d
Thanks in advance!

Answer 1

Did reinstalling help? If not, then consider reinstalling Lion on a newly formatted drive. Let the system reinstall using Internet Recovery instead of reinstalling from a USB flash drive. The downloaded installation will be 10.7.2.
Install or Reinstall Lion from Scratch
If possible backup your files to an external drive or second internal drive.
Boot to the Recovery HD:
Restart the computer and after the chime press and hold down the COMMAND and R keys until the menu screen appears. Alternatively, restart the computer and after the chime press and hold down the OPTION key until the boot manager screen appears. Select the Recovery HD and click on the downward pointing arrow button.
Erase the hard drive:
Select Disk Utility from the main menu and click on the Continue button.
After DU loads select your hard drive (this is the entry with the mfgr.'s ID and size) from the left side list. Note the SMART status of the drive in DU's status area.  If it does not say "Verified" then the drive is failing or has failed and will need replacing.  SMART info will not be reported  on external drives. Otherwise, click on the Erase tab in the DU main window.
Set the format type to Mac OS Extended (Journaled.) Click on the Erase button and wait until the process has completed.
Quit DU and return to the main menu.
Reinstall Lion: Select Reinstall Lion and click on the Install button.
Note: You can also re-download the Lion installer by opening the App Store application. Hold down the OPTION key and click on the Purchases icon in the toolbar. You should now see an active Install button to the right of your Lion purchase entry. There are situations in which this will not work. For example, if you are already booted into the Lion you originally purchased with your Apple ID or if an instance of the Lion installer is located anywhere on your computer.