Can't rarrange menu items

Hi All,

I have a multisite install and a selection of WPMU Plugins with a couple of others.

I have upgraded to wordpress 3.6 in the hope it would resolve but the problem still remains.
No javascript issues are showing in the console and a google search hasn't helped.

I have tried turning all plugins off and default themes with no sucess.

When on the menu's page the drop down help and screen options don't work and I can't rearrange the order of the menu items.

I know it's not really WPMU products related but I'm hoping someone might have experience of this issue and be able to point me in the right direction.

Thanks in advance for any help.