Hi datnoid,
Has it come back at all?
With the vertical line you've described, it definitely doesn't sound like anything the software would cause. When the line was on your screen, did it appear in the forefront of every window? Did you see it during the boot process (on the gray screen)?
Typically lines on the display like that are caused by one of a few things:
1.) The LCD panel
2.) The LVDS cable that connects between the main logic board and LCD panel
3.) The MLB / GPU (which is a component of the MLB)
I've also seen a few scenarios, in cases where the lines appeared on an external display (only) that the adapter was the issue or the port (Mini-DVI) was the issue.
Regardless, typically it's a hardware issue and as such would require a hardware repair for a resolution. Is the unit still covered by Applecare?