Hi, I have the same error. I am using Joomla 3.1 and JS Jobs jsjobs_j3.zip son no issues with that.
The error :
1062 Duplicate entry '' for key 'PRIMARY' SQL=INSERT INTO `cos_js_job_config` (`configvalue`) VALUES ....
Checking the database, the table cos_js_job_config indicates that there might be a conflict with the
indexes. Attached the screen shot.
Thanks in advance for your prompt respond since my JS Jobs is now blocked
PD: After doing some test, I found how the error is generated (from the user pov):
1) JS Jobs installed
2) JS Jobs configuration done. Save close.
3) Work on templates, modules, etc.
4) Open JS Jobs Component.
5) Click on
Admin -> Activate/update
6) The error is generated ;-( and JSJobs gets blocked.
From there the Component gets blocked.
Hope this helps.