DirectAdmin - Debian 6 upgrade DNS Issue

I have a Debian server, and today upgraded the server from Debian 5 to Debian 6. I followed the instructions here: [login to view URL] Everything seemed to work fine, however one of the sub DNS accounts - i.e. not the main DNS accounts, but a DNS account for a reseller has stopped working. The main IP address is: ping [login to view URL] is working OK, but the sub DNS account: ping [login to view URL] is not working! I am hoping someone who is clued up at DNS on Debian / Direct Admin can help me fix this - I need this fixed within the next 2-3 hours ideally, so I am online waiting to award someone this project!!