Have you tried to lower the broadcast quality? I only ask because if there was something in the update that put a min 3mbps on the upload that must be at the best quality. Have you tried UStream to make sure Twitch is not just flaking out? Keep us updated.
nothing is wrong on my end so im going to have to agree its on twitch's. we all got the error the same day and i streamed for quite some time the day before. now all of a sudden it flags an error and stops stream immediately. keeping my fingers crossed. i would hate to have to transfer to ustream cause of this