Very Strange User Behaviour

OK – I’m having a wierd issue. I can log in on multiple computers / multiple browsers and W3 Total Cache works fine for me. A colleague of mine (my server tech) tries multiple computers / browsers, and can’t choose options in any select box – they are all grayed out, and nothing drops down on the select boxes. This is across PCs, Macs, iPads, and three different browsers.

We are using the same user to log in.

It works for me, not for him.

What in the world could cause something like that?

https://wordpress.org/plugins/w3-total-cache/