Not sure what I did

Fusion was working fine, then suddenly I can not get the 2D or 3D views to display anything and there is a red boarder on the windows when I select them.

Obviously I did something.

Is there a config file I can delete or something to get back to the defaults that work?

There are a series of buttons next to the play controls, one of them probably says 'none' right about now
That is the red box indicating fusion is in 'none' render mode. Toggle the button for some-all-none..

None is good for cleanup without processing, all will process every node regardless if you need it for render (great to render thumbnail for all your loaders without having to view them) and the one that is used in final render is called 'some' and that's where you should live most of the time.

Some essentially just processes what is required for the node your displaying, nothing else, no loose branches, or downstream tools.

The default hotkey to toggle Some/None is Scroll Lock; for whatever reason I find myself accidentally hitting it a lot.

Great, thanks guys. I did not want to wait till I got to that part of the manual where no doubt I would have figured it out.

Now I can get back to messing around and gettin' through the docs and tuts!

Thanks!

Is there a way to change the hotkey from SCR LK because that key is used to activate the back light on my keyboard, otherwise I have to leave the back light off which makes it almost impossible to see my keys. I've tried going through the hotkey manager but it doesn't appear there.

I don't think so.
But you can activate your backlight and then manually within the interface set the Update back to Selective (Some).

I did try that but unfortunately it turns my back light off with it.