I hope this isn't confusing :
I am now temporarily running a master server on the old IP address (the connection has been restored). I'll do that for a while (a day or so) until nearly all DNS servers across the world have been updated to the new address.
So just for now, you can still use version U and the U hosts will still be able to find the master server. But more to the point, if your ISP has a slow DNS update, you can still use your version V to race on those hosts which are still connecting to the old master server. Just remember : you may not be able to find the host you were looking for, as every host is only on one of the two master servers.
This is only temporary - and allows some people to race who would have been unable to do so.