Apple software update popped up on my Macbook running OS X Leopard yesterday and prompted me to install the 10.5.5 update. I did so and after restart found that there were black boxes showing around various icons and the shortcut to Macintosh HD on my desktop.

This bothered me somewhat so I googled around to see what the problem might be and came across a post on Red Sweater Blog about a similar problem:

So … if you googled your way here after installing 10.4.8, and want to lose the damn rectangle. Let me review:

1. Open System Preferences
2. Go to Universal Access pane.
3. Switch to the “Seeing” tab.
4. Click the “Options” button for the Zoom section.
5. Turn off the “Show preview rectangle” checkbox.

So I checked these preferences on my machine but found the “Show preview rectangle” checkbox was already turned off. Further searching on the topic found no other help so as a last resort, I tried enabling Zoom, turning the checkbox on, then closing System Preferences. Then, I followed the instructions from the Red Sweater Blog again to turn it off and hey presto - no more black boxes.

Thought I’d share in case anyone else is perplexed with the same issue.