Unable to add host in VC

Hi,

I've installed ESX 4.0,  in  DMZ net work.

When I tried to add this server in Virtual center I get  "Request timed"  out error, but Im able to manage this server using vSphere client  and able to connect using Putty.

Im able to telnet 903 from VC server also from where I installed vSphere client.

any help would be highly appreciated.

Thanks,

Ajesh