Hi Dom if Russ's suggestion hasn't helped, I'd point the finger at the Qmaster underneath the legacy compressor v3. The symptom of the "submit" button is unselectable or "greyed" out usually indicates this.
Assuming this is compressor version 3.x and not the current v4.0 ...
You basically need to :
1) in compressor.app ver3, "reset background processes"/ cancel and don't restart. This is optional and is may not respond. Do this before getting the big stick out...
If you're using a managed cluster then use Qmaster administrator to remove any clusters that are used by the current node / host u are on. My guess is you're not and maybe using a quick cluster.
2) using apple Qmaster though the old system preferences pane.. Do these things...(a) In the "advanced" tab determine the path for the cluster storage. Unless you changed it yourself it defaults to "/var/spool/Qmaster" then (b) simply STOP apple Qmaster by Simply untick the "share this computer" in the "setup" tab. Close the prefs pane.
3) stop the compressor 3.x application
4) check the /applications/utilities/activity monitor.app for any residual "compressord". If any are there just force them out..
5) save any of your personalised qmaster settings if u can. Copy them elsewhere . U can reinstate them later
6) go and delete the Qmaster cluster storage the U determined in step 2.a. It will be the directory "/var/spool/Qmaster"
I'd say if you've undertaken Russ's suggestion the other compressor parm files etc have been cleaned up.
Basically you have no Qmaster running now... So judiciously start it again.
Save some time n Have a look at this old compressor v3 forum post for a detailed work instruction
https://discussions.apple.com/thread/1944194?answerId=9222102022#9222102022
Post your results here for others to see.
Hth
Warwick