Are you both connected to the same router?
(And I recently opened a Tech support thread
here)
EDIT: Missed the part where ya said ya were able to play b4.
What are the settings on both parties? Did his firewall change? Is he really playing the correct version? i.e. Did his profile switch to one of a different version and not notice? Is the router settings correct? Are you using direct Ethernet connection?
What is the set-up? Is your friend really connected correctly? Did his wireless/Ethernet card change settings? Is the game directory correct for the map? Are you sure the local play settings are correct?