Yeah I had that problem before. Go into your steam settings. Most likely it reseted your connection settings. Find the downloads tab and select your modem type. (e.g. dsl or cable). It should reset your game settings also. If not just type rate in console and set it to something along the lines of 35000. I'll double check right now so expect and edit on this post.
well the error occurs with the voice chat causing a buffer overflow because the rate settings in the client are set too low to accept all of the com. Setting the rates to whatever is your connection setting usually fixes the problem.
You'll know this is the problem if you watch the console and see a lot of voice receive type errors.