Gremlin in Excel

Excel suddenly started doing it's own thing??
opens new spreadsheets,opens menu's etc.. completely randomly.
thought it was a bug so ran Norton but found nothing.checked macro's and again nothing.
Can't really think what causes this and looks theonly way out is re-install.
anyone come accros this.

working in a support center I realize this is weird but it really does what it wants when it wants without any pattern???????

thanks a lot

Nicolas