Admin Backend -> Component install problems

[wooly]

Hi

Something wierd has started to happen.
I get returned to login when I try to install a component in the admin backend. This happens when I click the component install/uninstall link on the tool bar.....other toolbar links work but this sends me straight back to admin login....

I do get a 'very brief' message in my browser before I get to admin login page.

I have no way of copying the text as its so quick but I managed a quick screen grab and have attached a gif of the message.

Hope someone can help me

Thanks