If I log out & login again I am able to launch eclipse without the previously mentioned error. I am using Ubuntu 12.04(64 bit).
This message is because there is a previous Eclipse process hanging around interrupting the one you are trying to launch.
ps aux | grep eclipse
find the eclipse process that's still running. I killed both the
/usr/bin/java processes. The process number is the number immediately adjacent to your user name. Then run
kill -9 [process number]
(without the brackets). That oughta do it!