Have you tried to leave a comment on someone’s space and had problems? I have. I got the low down on what’s going on from my buddy Brian.
You might try to leave a comment and find the comment section "grayed out". (see the attached picture)
You can workaround this by clicking on the Signin button (which will sign you out!) and then signing in again. I’m told that the Spaces team is working on a fix for this and it should be working normally again Real Soon Now.