the workflow job (in central admin) progress is showing 0% and the status is paused since 3/04/2012. I've tried manually starting the job (by clicking on Run now) but it is still stuck.
Is there anything else i can do?
The problem lies with the Timer Service Configuration Cache. You need to clear the cache on all servers in the farm and start the SharePoint Timer Service(OWSTIMER.EXE) manually.
Steps involved in doing so is mentioned here.
If its a production environment just ensure you do the activity in the application servers first followed by the WFE.
Maybe you can see this :
http://sharepointtraps.blogspot.com/2011/10/timer-job-stuck-at-0-progress.html