>>>I am not going to fix all other forms, unless I'll get a task for that, though.
>>
>>So you have changed it to the syntax I suggested (which was the one I know).......
>>I'm going to look at the docs and see if I can find any reference to your previous version.
>
>Right. Although I took that suggestion from StackOverflow where I also asked that question and who eventually helped me to find the culprit :)

Looked again at the docs but cannot see anything that implies your old method was working. OTOH I did find an example here:

http://stackoverflow.com/questions/16529825/angularjs-ngclass-conditional

See the answer with 15 points....