RPC Terminates on connecting to Internet

I’ve installed Win2000Server on a system to be configured as a streaming server. Within a few minutes of connecting to Internet, the RPC service terminates. Microsoft says its resolved in SP4, but problem persists even after SP4 installed. Connecting to local network works fine. As soon as i connect to the internet (via DSL router/modem) RPC crashes. Anyone know how to fix this? All dependent services stop….the only way to have a functional system is to reboot it.