Yes Mark, Even I had faced the same issue earlier and I had to reset the chnages by downloading jobs from Version tool and it seems that there is no option to unlock the table other than deleting the workspace . I am waiting for other community member to reply on this .
In this situation I would delete the workspace which would release the lock and start all over again with a new checkout.
Hi, I got the official BMC answer -
"To discard changes made in a workspace, highlight the folders/jobs you want to revert and click the Unload button. This will remove them from the workspace without saving any changes that were made, and thus the latest version of the jobs will be the one that was last chacked in to the EM database. If you did check in the jobs at some point during editing, then the version tool is the only way to revert the changes."
(With thanks to Michiel).