[JamesAB]

It seems to be related to the contents of headinclude

By converting back to the default from the "Default Style" it makes the menus work again.

I'll try to track down the differences now.

--------------- Added [DATE]1483806663[/DATE] at [TIME]1483806663[/TIME] ---------------

I think it turned out to be a javascript problem.
I had been using async when calling some scripts, but some browsers don't seem to like that anymore.

<script async type="text/javascript" src="$stylevar[yuipath]/yahoo-dom-event/yahoo-dom-event.js?v=$vboptions[simpleversion]"></script>
<script async type="text/javascript" src="$stylevar[yuipath]/connection/connection-min.js?v=$vboptions[simpleversion]"></script>

When I remove the async directive things seem to work in all browsers again.