For those saying things like 'you're uploading wrong', you are clearly missing the point that iTunes Match users should not have to p*ss around with logging out/in again to get it working. It should 'just work'
I am a second time subscriber to iTM, the first time round, absolutely nothing would upload, and Apple refunded my sub, I waited another year, then bought another sub, this time, my library of 17000 songs uploaded initially without a hitch, but that was a few months ago, since then I have had the exact problem described above, the load bar sticks on 'uploading remaining songs and artwork'.
I am now really starting to wonder if Apple can actually manage web based services, and if they even have the competency to offer them.. first MobileMe, then Maps, now this..