I had this problem too with dota 2 test. Now I'm going to download the update again to dota 2
I got the same problem.
I play at home (view match only - weak computer), and at two internet cafe.
It is tedious because the game picks the default setting for me and I have to change the whole thing every time I play (not much time but it is really stupid).
It happened recently since I deleted my user profile on Steam at my home computer. I restored the files but it still happened.
Please help me.
Sorry for double post but I think the reason is Steam Guard system.
I deactivated and it didn't happen again. But no trade...