Exception setting "ViewEntireForest": "Could not find any Domain Controller in domain myoffice.local

Tried to run Exchange 2007 server EMS(Exchange management shell), and most of time, I got this error:

Exception setting "ViewEntireForest": "Could not find any Domain Controller in domain myoffice.local. The myoffice.local is up and running and all other machines did not complain the main. I run nslookup against this domain in the exchange server without any error. I remember I can use the lmhosts file to define the location of the domain, so I put a line below in the end of the lmhosts file, and it fixed my error:

192.168.1.20 MylocalDomain #PRE #DOM:myoffice.local