Maybe try to change the Steam server.
Just tried switching to a few different US and European servers. Also tried switching to the regular client, then back to the beta. Didn't help.
Steam support's website is terrible, BTW. There simply isn't a category that matches this issue. I know what will happen already: I'm going to wait several days only to have the support guy respond with an unhelpful canned response that pushes me to the back of the queue.