I tried repairing disk permissions but that didn't work for me. What DID work was a free download of Compressor Repair 2.1.1 which you can download from http://mac.softpedia.com/progDownload/Compressor-Repair-Download-45934.html.
I ran the program, waited 30 secs as it suggests then restarted Compressor 4. I then found that the submit button was no longer greyed out and I could convert files successfully.
Lots of posts out on this forum about this!. (greyed out submit). here's a detailed post here https://discussions.apple.com/message/17356372#17356372 ....It's likely your cluster infrastucture (including the inter communication between the components ) has not initialised correctly. There's a simple way to see this. Simply whilst in Compressor.app V4 try and mount your cluster storage (+shift+m). If the cluster storage doesn't appear in the list you just need to kick the QMASTER components in the pants.... (see here)
Definately no need to repair disk persmissions and all that stuff unless the app has some access issues. Doesn't hurt though...
Why?...well Incidently, QMASTER and COMPRESSOR.app V4.x now keep their state information in the users home directory at ~/Library/Application support/Qmaster and ~/Library/Application support/Compressor so under Lion 10.7.x, a REPAIR DISK PERMISSION operation WONT HELP YA at all as I beleive it doesnt work over the /Users/... paths.. (I'll stand corrected as always)
As in the post by akg10tb, you can do this yourself by following the post at:
post your results so that others may befeit.