I keep getting kicked from the server with the message that I lost connection to steam. I can immediately rejoin, but then my unlockables are unavailable. When I restart steam, it works again, for about 15, 20 minutes.... :S
didn't do any big changes to your computer or your internet?
googled your problem and strangely i didn't find a real solution... a few of them say its a problem on steam's side (though most posts are kinda old) if so then I guess you'd better send a mail to steam support or something like that..