Extreme zoom in/out

Hello,

I'm having a weird problem with the mouse wheel zoom in Solidwork 2013.

The zoom works fine, until, at some point, the zoom goes extremely far in or out with one touch.

I'm working with two screens and I have found that when I click on the Windows desk and click again on the Solidworks part or assembly, the zoom works fine again.

What could be the cause of this?

Thank you

Chad ML

SolidworksGeneral