In Excel 2007, when I click on a cell, it arbitrarily selects several
adjacent cells as well. If I touch a directional arrow on the keyboard to
move (for example) up and then back down to the cell I want, it lets go, but
this is a major nuisance. It's also happening to two other people I work with
and we're all in different files. Why does this occur and how can I make it
stop? Is it a bug in the software?

Thanks for any help you can offer.