Internal Website name resolution problem

We are having an issue with our name resolution to an internal citrix webserver called isis.com. It should be pointing to 172.16.64.67. We have it listed correctly in our Dns and until this morning all was well. Sometime last night changed and it stopped working. If you type in isis.com.hamiltonmrdd.local (hamiltonmrdd.local is the name of our domain) it works fine. If you do a nslookup on isis.com, it comes back with the correct information

We have two websites setup like this. One is isis.com the other is isis-test.com. Isis-test is working fine (this is on a separate server). We also tried to have another webname associated to 172.16.64.67 called isismrdd.com and that worked fine. We have tried a dnsflush on both the dns and the computer having the problems. The only thing we havn't tried is setup isis.com to another ip address. I'm not sure what else to look for. Any help would be appreciated. Thanks