This little window popped up while I was away. No idea what it means

It means that Windows Aero is not fully loaded, which is needed by a folder portal. Just reload the windows blind skin or change to another one manually. Now it is fully active and portals can be used, sadly all icons gets kicked out of normal fences (at least happens that to me).

It's telling you that Aero is not enabled. If you have installed IE 10, that would most likely be the problem. Uninstall IE10 and KB 2670838 and you should be good to go.

It means that DWM (desktop window manager) isn't running.

Go to the start menu, type services in the search box, find desktop window manager in the list, right click it, choose restart.

You only got one? Count yourself as lucky.

https://forums.wincustomize.com/436519

wow, thanks folks.  I don't have IE10. Don't use IE at all, although I did use it yesterday, IE9, to help my Dad troubleshoot a bad add on, so that must be it. Haven't seen it since. Don't know why it waited so long to pop up. But thank you.  If it happens again, I'll know what to do.

and OMG Wizard that's crazy!

FYI the screenshot is clearly showing the DWM is working just fine, notice the shadows.

Make sure you have the latest version of Fences.  I imagine you either ran a game, applied a new theme, upgraded your video drivers, logged in via remote desktop, or one of the other things which causes the DWM to shutdown briefly.

Hi Neil... I have the latest version of Fences and the only thing on your list I have done recently was apply a new theme, but that was yesterday. The only thing on your list I have done today is play solitaire for a bit

Now that I am aware of this, I will keep an eye on things.  It's only happened once, ever.  So may just have been some weird glitch.