Hi gnholcomb2,

Are you using the AdBlock add-on by any chance? I searched online and found this related thread that suggests the problem is related to this: https://support.mozilla.org/sv/questions/941739

You could try to start Firefox with add-ons disabled (you can do this from the help menu) and see if Yahoo Mail loads fine then.

Hope this helps. Good luck!

- David

I had the same problem, I installed a newer version of firefox, but it still did it, so I went into the add ons on firefox and disabled babylon (do you happen to have that in your add ons?). Anyway after I disabled that the problem had gone. I hope this helps you.