I have done a bit of trawling through the RRE forums regarding my lagging problem. It seems it is something that affects a lot of people in RRE multiplayer when they can play other sims online without problem.
It stems from the way multiplayer works in RRE & my problems are probably caused by a slow upload speed (0.35MB/sec in my case, compared to 7MB/sec download). In other sims like GTL & GTR2 a player's PC sends out just one packet of information regarding his position on track to the server which then distributes that info to all the other players. RRE doesn't work like that, it requires that each player has to send out a packet of info to every other player individually, so for Norisring my PC needed to send out 15 packets of info instead of the one in GTL & GTR2. Don't know how many times per sec it has to do this, but it appears that my upload speed is not adequate for all this information.
So it looks like I need to upgrade to a superfast internet connection to be able to race RRE online. It has recently become available out in the countryside where I live, so I may see about upgrading. This RRE is becoming expensive!