OK I think using tbworld's suggestion I have been able to find the problem (THANKS again tbworld :up: ).
The error console is saying that an
image is missing, yet no image was provided with the download. It is called
trans_40b.png.
You can find a copy of that image here:
http://www.sega-16.com/forum/images/buttons/
Install it to your buttons folder and you should be golden.
Other than the 'new line' feature
not working, everything else is fine on 4.2.1.
Also, if anyone wants to learn how to search for javascript errors like this with their browser, I found a great tutorial here;
http://codex.wordpress.org/Using_You...aScript_Errors
.