Why does my mouse have intermittent clicking issues?

I'm wondering if this is a hardware problem with my mouse or some sort of setting which has gone wrong. Using an iHome optical mouse connected via usb.

Problem: Often (not always) when I select a file or files in a finder window by clicking once with my primary button, instead of just selecting that file (or app) it opens it. This is a problem for when I want to select multiple files to relocate or reorganize.

I went to the mouse settings and could seen nothing amiss there. This just started happening yesterday