I encountered a really strange issue I hadn’t seen before on my backup box. While in my desktop, I suddenly found that anything with text was missing certain areas and then as soon as I dragged my mouse over it, it would reappear, only to disappear after moving the mouse away from it. It took me a while to discover the fix for this as I was occupied with building systems for other people at the time. Here are a couple of pics to illustrate the peculiar problem:
Firefox                     Opera

I created a second user to see if it was a system wide user and I first I thought it was only a user issue, but once I started changing themes around, it did the same thing with the other user. I thought it might have been the themes but then since Arch had upgraded some fonts lately I decided to look under Desktop > Preferences > Font and see if I had selected a custom font that was odd. Once there, I noticed that the “Best Shapes” selection was chosen. I changed the selection to “Subpixel Smoothing” for LCDs and then suddenly the disappearing text went away. I had changed the monitor on that box to an LCD about a month or two earlier and never thought to check that setting. It’s amazing how something so minute can make sure a difference. I always like knowing what the actual solution is. Hopefully this may help someone else. Cheers!