I know this is a bit redundant, because this info has been posted in several different threads, but when I read that Rich Lee had experienced the same issues during the race, I figured I post the solution here as well.

In multiplayer.ini file, change this...
Auto Join Chat Server="1"
To this...
Auto Join Chat Server="0"

Also, Change Matchmaker.rfactor.net address to =127.0.0.1