Having the same problem. Everything was fine yesterday afternoon prior to 7pm. I was playing music from the cloud on my MacBook Pro and had played music from the cloud on iPhone 5. I went out around 7pm and when I came back at 930pm, my MacBook Pro had all cloud music greyed out and the cloud indicator next to the button to choose Music/Movies/Podcasts had the lines going through it and said "Accessing iTunes Match." It never budged from this. I did Store > Update iTunes Match which seemed to do it's thing and complete, but then the cloud indicator would still say accessing iTunes Match and eventually stop with the lightening bolt through the cloud.
Same thing this morning. I went to my Desktop PC running windows and find the same issue. Updated it to iTunes 11.1 and restarted. Same issue. My Windows laptop has the same issue. I called Apple and the guy on the phone was convinced it had to do with DRM and my content not being authorized to play, so he had me deauthorize this windows laptop and reauthorize it. Still same problem. His recommendation was to go home and do this on my Windows desktop, which is the "primary" machine where I originally set up Match from and can see all of my local media stored on my NAS. I'm not convinced this is the problem, especially after seeing all of you with the same issue.
My iPhone 5 is working fine and streaming all music from the cloud.
This was working fine, with iOS 7 and iTunes 11.1, on at least my iPad, iPhone, MacBook Pro, and Windows Laptop yesterday until it crapped out last night on the desktop/laptop devices.