When I try to use my ArcGIS program the program does not open and instead says ArcGIS for desktop has encountered a serious error and is unable to continue. This has never happened before and only started yesterday. I did send an error report to ESRI. Tried deleting the ESRI key using Regedit, but that did not work.
This was caused by a bug between Python and ArcMap 10.3. The solution was to pull up Regedit and navigate to Software>WOW6453Node>Python>PythonCore>2.7
2.7 needs to be renamed as 2.7-32
This fixed my problem. Hopefully this can help someone else.