Which platform? If Windows, I think I fell into the same trap once. FMS installs its own Java system inside its Program Files; you should use that one for the Admin Client.
Today I couldn´t open the FMS 10 console and just saw this article from last Friday (Knowledge Base), that apparently is affecting Mac OS 10.6.8
I´ll try the Java update link tomorrow because now there are some users ....
Hope this helps.