problems after installing wordpress 4.0

I’ve just updated to wordpress 4.0 and a handfull of things have stopped working in my admin.

Most of the features are still working, except a lot of buttons no-longer work. For example, if I open the widget section everything appears fine, but if I click on the buttons nothing happens.

Same goes for the customize-appearance section, it opens and I can see all the options, but nothing happens when I click on the buttons.

Almost everything else is working as normal, just the buttons in these sections are giving me trouble.

Has anyone else experienced this, or have any suggestions on what to do?
Thanks in advance