Thanks for the reply, Mel. Unfortunately, it didn't fix the problem. I have not been able to upload anything, so far, not even any of the simple examples.
There are also some issues with the LEDs on the Cube. For example, using the Serial Monitor, the 'all red;' command turns all the LEDs off, but the 'all green;' and 'all blue;' work. And sometimes level 1 works and sometimes it has the wrong colour. I had another look at it, and I believe the red is not working at all on level 1. I expect I should look elsewhere in the Forums for these answers.