I recently downloaded Ext JS 5 to add to my XPages applications. La dee da, create new application, download Ext JS 5, import into application, do some stuff, close Designer, re-open Designer, attempt to re-open my app, and BOOM
Now I can’t re-open my application. Ext JS5 has a lot of elements straight out of the box. If you add the whole thing, you’ll likely blow up your application. The worst part is that once you get this error, you can’t get back into the application in order to delete elements you don’t need.
So either back up your application before adding stuff, or you use source control, or be sure you aren’t importing too many elements.
For Ext JS Grids 5, I recommend just the build folder (and it’s direct level contents) and the package folder within the build folder that includes the theme you are using.