multisite error subdomain not working

I am running wordpress 3.01 on shared hosting.. I installed multisite and can see superadmin area… I added couple of sites just to check if it’s working or not… it workd!!then i went to bed and following day nothing worked!!.. i tried adding 1 more doman.. testing.domain.com and it’s not working… can someone help.. thanks..

i am getting following error

“Your requested host “thisistest.mortgagepress.ca” could not be resolved by DNS”