Using Mouse selects more than 2 cells Excel 2007

[Mark]

When I use the mouse to select a cell it selects 2 or 3 cells, what can I do
so it will onll select 1 cell. never had this problem with 2003;

 

[Dave Peterson]

Do you see EXT (an indicator that you're extending the selection) in the
statusbar? If yes, then click F8 to toggle it off.

Have you tried a different mouse?

Or gently banging on all the buttons--including the wheel mouse button?

Sometimes, those buttons can stick.