Not sure quite what happened, but somehow it's fixed it.
It may have been Internet Explorer's cache that was the problem. Unfortunately, I don't think the cache had fully cleared after doing just that step and testing.
I had problems importing into my Update Site so had deleted and recreated it, somehow choosing 8.5 version. So that also was not loading the 9.0.1 OpenNTF version. After I fixed that it was working. After disabling that feature and switching back to 9.0.1v00_00_20131004-1200, it's still working.
Thanks for mentioning clearing the cache, I'll make a note of that for the future.