Well, based on the details provided, you are running a MacBook Pro with Mac OS X 10.6.4.
iCloud is known to work BEST with OS X Lion (10.7). This might not be the issue, but it's worth looking into. iCloud has limited support for Snow Leopard and below.
I, personally, don't have iTunes Match in the cloud because my library is too large, but whenever I tried accessing iCloud services before I upgraded to Lion, it was tricky and annoying.
I hope I helped, or at least got you moving in the right path.
There are more drastic things to do to your library when things go bad, but as a first start, I think updating everything as far as you can is the best first-round solution.
If it doesn;t work, let me know and I'll help you further.