My iMac cursor turns into a 1/2" square made up of small lines. There are also very thin lines on different portions on the screen.
iMac, Mac OS X (10.5.8)
Sounds like a hardware error in the graphic card. When you make a screenshot with the thin lines, do you still see them on the screenshot?
I have the same problem. I can't see the cursor when I take a screenshot using Grab utility.
Try trashing your Desktop preference file. You can find the file here:
Macintosh HD> Users> Your Username> Library> Preferences> com.apple.desktop.plist
Drag the file com.apple.desktop.plist to the Trash. Empty the trash and restart your iMac.
Good luck.
My cursor turns to a square
