Random "Columns" of terrain sprouting up..

[Wiltron]

In-Game, at random times throughout the course of playing the game I see a column of terrain stretching from the very farthest side of the map to the other side, cutting through anything like buildings or terrain hills. It is usually 1 pixel thick and I can walk/fly through it, and on the other side I can see the same thing. The width/height of the "Column" of terrain, could be anywhere from the height of my character, to the height of a tower in Stormwind. Also, it can go lengthwise along the floor of the terrain.

It appears like a small bit of texture, usually local to the area I'm in, has been stretched from one side to the other. So, if its in Stormwind, it looks like the one of the gray bricks has been stretched really thin. If I'm in Uldum, it's usually sand or something. I wish I could post a screen shot, however I had deleted the game installation in an attempt to fix the issue, and lost the screen shot I took.

Now, as per my knowledge in computers, I'm not an idiot or a nub. I'm a licensed A+ certified technician, with my MCSE, MCSA, CCNA and Network+ certifications. I've run out of ideas, so I'm turning to MMO-Champion.

Here's what I've done to try to fix the issue:

Cleaned the computer physically with compressed air, and even dismantled the fan assembly, and cleaned it and re-greased the bearing
Replaced the fan assembly
Reseated the memory
Format and reinstalled Windows, reinstalled the game via discs, reinstalled game via downloaded client from b.net
Ran game without add-ons, and using compatibility mode, with and without admin mode. Also tried variations of using the compatibility mode options to disable windows features.
Ran memory diagnostic tests, HDD Tests, Graphics card burn-in tests, all of which passed without warnings of temperature getting high
Cleaned and reapplied thermal paste, using Arctic Silver 5 series, on both CPU, Graphics and Memory cooling slots.
Applied a "Cooling pad" underneath the system.

Current computer setup is:
Core2 Duo 2.0GHz
4GB DDR2 667 Ram
nVidia GeForce Mobile 8600 GT
Windows 7 Ultimate (latest drivers, BIOS, Windows Update, and all that fun stuff)