From KB1014213:
When trying to update host data, you may experience these symptoms:
The vCenter Service Status shows the error:An error occurred, please try again in another vSphere session.
The Hardware Status tab shows the error:An error occurred, please try again in another vSphere session.
From: KB1013893
The VirtualCenter Server Service Status fails with the errors:
Cannot access the health service!
Login to the query service failed
Do not have permission for this command
The solutions mentioned in both the KB articles didn’t solve the issue for me. In my case name resolution was the problem. We use another domain for our vCenter server. The clients where not able to resolve the FQDN of the vCenter server. So I added the FQDN and ip address to the hosts file. After this little change and reconnecting the vSphere client, everything worked as it should be.
ICT-Freak.nl 
instead of changing the LMhost file, can we add connection suffix instead?
Nice. Adding an entry in hosts file in the client machine did the trick for me as well. We use vCenter 4.1
VERY SIMPLE. go to Configuration tab then on software properties click on DNS and Routing and it will give you the DNS and routing properties. Click on properties link and modify the domain to your appropriate domain name and host name also your primary and alternate DNS server IPs