Error - The resource you are looking for has been removed, had its name changed, or is temporarily unavailable

Press F12 and click "Empty cache and hard reload"

Thanks for that.  I have found it works, but I wanted to know what causes the problem.

What link to you or your users use to access your Innovator? Does it contain the word "X-salt"? If yes, than this is your problem. 

Angela,

It happens when I am already in Aras too.  Sometimes it will happen when I am trying to create a new form, but works normally when I open an existing form.  It seems to be a bit random.  Thanks.

Have you checked the browser console for helpful error messages? It would be interesting to know "which" resource makes the trouble. 

Angela,

How would I check the browser console for this information?  I had a user have this happen to them when trying to log in yesterday morning.  I have had it happen when trying to create/edit forms.  The top half with all of the field tabs would give the error.  Thank you.

When you see the error, press F9 or right click into the browser window and click 'Investigate' (or similar - I don´t have an English browser). Then switch to console tab.
You will always see a lot of warnings and error messages there. That´s normal. Look for an entry that fits to your error message. In best case it tells you, which resource makes the trouble. 

Your issue reminds me to an scenario that once one of my programmers created by accident. 
1. Do you program your customizations in a test system first, and then export/import them to the main system after proper testing?

-> If yes: Do you use ItemTypes or form elements with own images and icons?

-> If yes: Are your icons located on vault or codetree? If you use vaulted images, this can create terror and chaos.