vsphere client -- connection failure ?

How can I fix my vsphere client
below error when trying to login ?
  ** A connection failure occurred unable
       to connect to the remote server

I can ping the server from the client machine,
therefore I know it is up, was able to login before,
tested with some other accounts, all account fail,
my ActiveDirectory & DomainController are up,
therefore everything should be OK.
  ** Maybe there is some type of
       local ADMIN user/pass I could try ?
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Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
A few tests...

Do you connect directly to the ESXi Host Server or vCenter Server ?

Have you tried connecting by hostname, fqdn, and IP Address ?

If you type http://<ip address of server> do you get a web page ?

Have you tried a different computer ?

if you type

telnet <<ip address of server> 80 does it connect ?

telnet <<ip address of server> 443 does it connect ?

telnet <<ip address of server> 902 does it connect ?

telnet <<ip address of server> 903 does it connect ?

if vCenter Server, restart vCenter Server service ?

if vCenter Server, is the service started ?

if vcenter Server, are you using SQL Server Express Edition, is the database greater than 4GB or 10GB ? check SQL folder

if ESXi, restart network management agents at the console

otherwise REBOOT server.

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Also are using the web client or installible C-Sharp client?
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