I/O button greyed out in Session View

[Comsat72]

In Live 8, the I/O "show/hide" toggle button is greyed out, or whited out, and does not work.

In Arrangement view it is normal and does toggle to show or hide the I/O controls.

I can't find this exact problem anywhere else, can anyone offer any help?

[rdevries]

close or resize the clipviewsection below the mixersection, if the mixersection is too small then the I/O button is greyed out.

[Comsat72]

So simple, but I would have never thought of it! Thanks for your help!!