Third-party extensions can provide some useful additional functionality to ArcMap, but are not supported because they have not been written by Esri. If ArcMap is not performing correctly, it may be necessary to remove/uninstall any third-party extensions you have installed to see if this resolves the issue.
There are two ways to uninstall Third-party extensions:
a) Via the 'Add/Remove Programs' section of your machine's Control Panel.
b) Using the Component Category Manager:
- Go to C:\Program Files (x86)\ArcGIS\Desktop10.1\Bin\Categories.exe (change 'Desktop10.1' to reflect your ArcGIS 10.x version)
- Uncheck the option to Hide ESRI Components
- Navigate down to ESRI Mx Extensions
- Look at all the objects within the Esri Mx Extensions folder. Ensure they don’t belong to any other software (i.e. they should be prefixed with either 'esri' or 'ESRIUK' as per the above example).
- If they do belong to other software, you will need to remove the extension by selecting it and choosing the 'Remove Object' button on the right-hand side of the dialog window.