MacBook Pro 17" 2.16 Ghz - Ongoing Shut Down / Freezing Problems

Question

After searching around the web for quite awhile and reading through as much as I can on here, I've finally run out of options and so thought I would post my experience / problem on here and see if anyone knows how to fix my problem.
My gear:
OS 10.6.7
MacBook Pro 17" 2.16 Ghz
Model Name:          MacBook Pro
  Model Identifier:          MacBookPro1,2
  Processor Name:          Intel Core Duo
  Processor Speed:          2.16 GHz
  Number Of Processors:          1
  Total Number Of Cores:          2
  L2 Cache:          2 MB
  Memory:          2 GB
  Bus Speed:          667 MHz
  Boot ROM Version:          MBP12.0061.B03
  SMC Version (system):          1.5f10
Video:
Chipset Model:          ATY,RadeonX1600
RAM - 2 x 1Gb Chips
FUJITSU MHY2120BH:
  Capacity:          120.03 GB (120,034,123,776 bytes)
  Model:          FUJITSU MHY2120BH                     
  Revision:          0081000D
  Serial Number:                  K439*****H4A
  Native Command Queuing:          Yes
  Queue Depth:          32
  Removable Media:          No
  Detachable Drive:          No
  BSD Name:          disk0
  Medium Type:          Rotational
  Partition Map Type:          GPT (GUID Partition Table)
  S.M.A.R.T. status:          Verified
  Volumes:
  Capacity:          209.7 MB (209,715,200 bytes)
  Writable:          Yes
  BSD Name:          disk0s1
Hard Disk:
  Capacity:          119.69 GB (119,690,149,888 bytes)
  Available:          98.97 GB (98,967,773,184 bytes)
  Writable:          Yes
  File System:          Journaled HFS+
  BSD Name:          disk0s2
  Mount Point:          /
Problem:
Over the last few months I've had constant problems with freezing, shut downs. This might be in the form of I'll be working in iMovie editing some video and then mouse down into the corner to switch Spaces, the screen will half zoom out then just hang. Mouse won't respond, everything just sits there. I usually have to fix this by holding down the power button until the MBP turns off, then just reboot.
Other times I'll leave the computer on at night, wake up in the morning and it will either be off and as such, I just have to press the power button and it boots up again. Or the screen will be off, metal above the Function keys will be cooking, but the computer isn't responding, just a blank screen. I hold down the power button until it turns off and then reboot again.
These problems were getting worse. It has gotten to the stage where it might freeze a couple of times a day.
Seems the problem only occurs when the MBP is working. I might leave it rendering at night and wake in the morning to find it off etc.
Will also sometimes get horizontial lines in apps. I shut them down and start them up again and it's fine. But it's like the graphics card is struggling big time.
Actions to Fix:
- Started with repairing the permissions, but I always found that it had lots of items to repair, would repair then, but then if I verified again, the same things would come up as needing to be repaired. I also tried booting from the OS X DVD and repairing from that version of Disk Utility, but same result.
- Created new admin user account, to see if problem was just limited to my account. Same problem.
- Ran AHT from the MBP DVD that came with the MBP and it passed the hardware test. Though I couldn't find anywhere to make it run an extended test. The test I could run would only take about 10 minutes I believe.
- Erased the HD and fresh install of 10.6.3 from DVD, then software updates  to 10.6.7 (yesterday). Repaired permissions after each step. After the OS upgrade I got a decent list of items that needed to be repaired, and after repair, would still show as needing repair. I checked the KB and it listed a lot of files that might get this error, but that it was ok to ignore them.
- Was editing video this morning in iMovie again, running Disk Utility on an external drive and boom, the MBP locked up again
I've gone through the /logs/crashlog in both the root and home user folders. After nearly all crashes these are empty, so it's not even reporting it anywhere.
Can anyone shed any light on whhat might be causing the problem?
<Serial Number Edited by Host>

Answer 1

Actually, when I was at the Apple Store I had both laptops flat, with the screens at 90 degrees. Pushing the screen forward and back with my fingers (via the top of the screen of course), the 15" easily has twice the hinge resistance. With that kind of test, weight isn't a significant factor -- that 17" hinge on a 15" laptop would probably cause the screen to come crashing down, too.
There were a few people in these forums who said their 17" was actually too tight (wish I had that problem!). It seems like a quality/consistency problem that could easily be fixed by A) measuring the force required to move the screen back and forth before screwing the case together, and B) making the hinge tension adjustable.