Mike, I am just setting myself up with sketchup and just beginning to use it. I was having this same problem with "orbit" and the scroll wheel. When I pressed the scroll wheel, it sent me out of sketchup and into some other application widow that was open on my desktop.

I have a Microsoft wireless mouse. In the device settings, the scroll wheel is set to "flip" (whatever that means) as the default. But there is an option for "enable program-specific settings." Here, I set the scroll wheel to "autoscroll," specifically for the sketchup program. Now, the scroll wheel works as sketchup says it ought to for zooming, orbit, and panning.

You change the setting for the scroll wheel generally, but that might affect how it works for you in other programs.

Hope this helps.