Custom calculation script disappears when selecting Edit - BUG???

I need to edit a Custom Calculation Script I wrote a few months ago in my form. I opened up the field properties, navigated to the Calculation tab, and I can see the script. I click Edit and the pop up window is blank! When I close this window, the script is gone.  This has happened **twice** now.

Is this a new bug? Any way to get the script back? 

I have the latest version of the application.