Another "me too", sorry... I've uninstalled iTunes, deauthorized my computer, re-authorized my computer, reinstalled itunes, turned off genius, turned it back on, logged in, logged out, restarted, yadda yadda, blah blah blah... No similar streaming services running in the background.
Sorry I couldn't be of more help. I rarely need to wait for the men in the white coats to fix things, but it looks like I'm going to have to just wait this one out. It really seems like a server error, and not anything on my end. Any "fixes" out there might just be flukes. I've literally tried EVERYTHING. Funny, iTunes didn't hesitate to charge my debit card, despite the fact that I've never had the pleasure of enjoying this feature for even one minute before it started being a problem. Shame on you, Apple.
"iTunes Match has encountered an error. Please choose Sign Out and then Sign In from the iTunes Store menu and try again."
over and over and over again...