If you have a deployment job that hangs in the running state where it had previous failed then try this:
on source and target please do the following:
Open Central-Admin - Operations - Timer Job Status.
Choose "Service" for the "View"
Select "Central Administration" for the Service
Can you find a Content Deployment timer job?
If not, then the job is indeed no longer running.
In this situation you can change the status to Failed manually to allow restart:
choose the list item related to the job that shows the incorrect status
edit the job and change the "LastStatus" field to "2" which means Failed.
Now you can restart the job manually using the manage content deployment paths and jobs page.
Thanks to Stefan Goßner