Mac Display Clarity Problem

I just went through troubleshooting a bizarre Mac display problem.

The symptom was that on my LCD monitor, the pixels coming out of the Mac weren't lining up with teh pixels on the monitor, so it would look clear on the left side of the screen, but fuzzy in two spots across the screen.  Seemed like a pixel clock type problem.

But I tried something this morning that ruled that out - I logged in as a different user.  The display cleared up.  So it was something configured for my user account that was doing this.

I went through ~/Library/Preferences looking for the likely culprit, and eventually just moving all the files that were there to somewhere else.  That fixed the problem but of course now all my preferences were gone.

After a bit of trial and error, I narrowed it down to one file:

Opening this file, I could see a setting called "closeViewZoomFactor" that was set to 1.001250.  So my display was zoomed in just a tiny bit, enough to just make the display a little bit fuzzy.

To fix the problem I deleted this file, and that made the display come up clear, but I had no mouse cursor.  To fix that, I used Cmd-Opt-F8 to turn on Universal Access, then Cmd-Opt-= to zoom in a bit and Cmd-Opt-- to zoom back out.  This brought the mouse back, and had me at 1.00 zoom.

The interesting question is, how did I get my system into the 1.001250 zoom state in the first place?