Hi
Check your vCenter and SQL server ( if you have it installed in same machine with vCenter) services on installed machine and see if they up and running.
or if your SQL is on other machine then first ping SQL machine and second go to see if DSN can see SQL machine or not.
ping AD as well to see if ADAM and AD connection works fine.
and funny thing is some times restarting machine make it magic and everything work again.
I had a VM vCenter that not working and i just restarting it and voila it back online again and never goes down till now.
Armin Lavaee
Go Virtual
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