Thanks a lot to Chris Miller for sharing this article at socialbiz.
More and more of you should be utilizing the Server Controller feature of IBM Domino server installs for some greater control in function and access to working with the IBM Domino server task engines. However, if the IBM Domino server controller crashes or somehow gets abnormally terminated without a proper "quit controller" command being issued, you may not be able to restart it.
You may attempt to restart the entire operating system to get everything back to normal, but before you take that step, there is another quick trick you could try. After the controller crashes abnormally, navigate to the IBM Domino server data directory. Find the file called .jsc_lock, and delete that file.
It is a remnant lock file on the process that did not get removed due to the server crashing.
Removing this file should allow you to restart the Server Controller normally again and put everything back to normal quickly.