Cura stopped working altogether

[Patchy 0]

Hi, after using Cura (with a Macbook pro) with my new UM2 Extended without significant problems since about 3 weeks, yesterday it suddenly stopped working completely. When loading a new file, it newly goes automatically into layers view. On selecting normal view, the object disappears. One can't select it, it doesn't show the print time, one can't save the gcode. This was 15 mins after using it successfully and without installing anything in between.

After many tries loading different models (which had worked before), I decided to delete the Cura app (V15.02.1 - sent app folder with all contents to the trash) and and installed the latest version (V15.04). It made no difference, still nothing works. However, I noticed it still had the settings from before (UM2 Extended and Cube printers installed - I was not able to find where these settings are to delete them - I thought a completely new installation would be best).

If anyone has any idea what I could try, I would be grateful, thanks.

[Patchy 0]

Update: It is now clear, the problem had to do with me being a newbie with Cura. I was loading gcode files instead of stl files. When I loaded the original stl files, it all worked fine again.