Highlight text

I am working in Microsoft Word and throughout different documents when I highlight text from time to time it will all get deselected and I have to reselect it again. Why is this going on and how can it be fixed? I use a wireless mouse and it uses a USB insert into my laptop. The brand is a Logitech.

You may not really have a hardware problem at all. MS Word can be overly sensitive at times, especially when performing a function such as highlighting text, and when this happens to me (which it does, from time to time) I just have to slow down and be quite a bit more exacting in my process.