Cells highlighting when clicking on them?

[Tom0822]

Hello...



I have Excel 2007 on a Win7 PC. When I click on a cell, it hightlights it and continues to highlight every cell I click on. Kind of like holding down the Ctrl key and clicking on the cell.
I thought maybe the Ctrl key was stuck, so I unplugged the keyboard and it still highlights every cell I click on.
When this happens, I can't click on any tabs either.
However, I opened up a new Excel spread sheet, clicked around and it wasn't a problem with it. So I close it and it resolves the issue. But this has happened a couple of times and happens randomly.
Anyone know what may be the problem?

Thanks