Once the few clients that are on the wrong chain are gone this shouldn't be an issue any more.

You can also do this. Start fresh and use the -connect (not -addnode) in the Config file or the startup switch

use these IPs

(Start up Switches)
-connect=37.59.48.89:7685
-connect=62.210.122.161:7685
-connect=107.170.113.225:7685
-connect=66.172.12.153:7685
-connect=192.99.35.133:7685
-connect=72.78.100.7:7685
-connect=178.238.45.216:7685
-connect=72.52.231.153:7685
-connect=74.105.241.83:7685

Once you are on the right chain, you can restart without the -connects.

So far i have 3 of 3 computers on the 500k chain, only 1 I had to full re-sync. The rest picked up on restart no problems.