It is hard to diagnose the problem when you don't say what you were doing when you got the error. What were you trying to do?
However - if you can't get into WAS Admin, that's a serious issue. If WAS isn't working, then nothing will probably work.
First - check to insure that WebSphere is actually running. The easiest way is to do a "ps -ef | grep java" and look for an entry with your WebSphere profile name listed in it (usually server1 if you have a default installation). If that isn't running, then go to step 2 below and check the logs.
If you can't get into WAS, you can go into the logs sub-directory of your WAS profile and look for SystemOut.log and SystemErr.log files and see what they say. Reading these logs can be moderately difficult if you've never done it, so check to see if you can get assistance from a WebSphere administrator.
Last, check under the /tmp/dsinstall/logfiles directory and in it will be a copy of your installation log. Check that for errors.