Screen changes but I don't want it to

I hope I can describe my problem adequately. An example: I was composing a new message on Outlook when suddenly, the screen changed to the Junk Mail folder. When I clicked the Outlook icon on the task bar, both screens showed in miniature form. I clicked the one that looked like the new message I was working on, and that screen appeared full-size.
At other times, I have been composing a Word document and the cursor would jump to a different position in the document. If I happen to notice it, I can move the cursor back to where it had been. But if I don't notice it immediately, I might type--whoops! It just happened as I was typing this message to MajorGeeks. The cursor moved out of this box and showed up in the upper left corner of the screen. I got it back okay.
I have run scans with Microsoft Essentials, MalwareBytes (?spelling) and SuperAntiSpyware and nothing bad was detected.
Any ideas?

 

I've had the same thing happen on my Dell Precision M70 workstation (laptop). It happens if I accidentally touch the strike bar located between the G, H and B keys on the keyboard or if I accidentally touch the track pad with one of my fat thumbs!

I've tried using the Alps touchpad software to no avail as it has no effect on the strike bar.

I guess it's an inconvenience we'll both have to live with.