It's happened to me once and with just one icon on my home screen. Mine occured after I was experimenting with a homemade multimedia dock with a strong magnet. I thought the magnet may have been the problem. Did a reboot and problem went away, hasn't come back but I have not used the dock again.
My Droid did that too for a few days, but all is fine now. For me it was that the icons were in the normal two rows, but not in a straight horizontal line, some were higher, some lower.