Esx host disconnect Vcenter

Hi,

i have a HP server which is installed ESX4.0.0 build 164009.once i connect the host to vcenter couple of minutes later its disconnect from the vcenter.

even though i restarted the management service. still same issue. If i access the host directly using Vsphere client its working.

Any one faced same issue. please help me on the same.

Thanks & Regards,

Srinivasan M