sometimes I get “this file contains potentially unsafe dynamic content” message in Mathematica notebook

Sometimes, when I open my own notebook, I get the message:

This file contains potentially unsafe dynamic content.

I do not remember when I started seeing these messages, but it was not long ago. May be 2-3 weeks ago? They do not show all the time. It is my own notebook, that I could close, go sleep, wake up, come open it up again, and I could see the above message, or I could not. Not sure what triggers it.

Here is a screen shot of one just happened.

I normally just ignore it, and enable dynamics and go on. I googled around, and do not see mention of it. One reference I found is this, where it talks about TrustedPath and such, and I really could not understand it at all.

This notebook just sits in my folder on my PC, same folder it was on all the time. May be an expert can explain this in easy to understand way, because I do not understand why I need to worry about the trustedPath thing when I am working on my own local PC (I am not even on a network, just stand alone PC in my living room) and what I need to change if any.

I'm using v8.0.1 on windows.