I've tried every Compressor reset/repair instruction under the sun in various combinations to get my renders to work in Compressor. It's often that my fixes won't work or won't work long, other times, a simple restart gets things back on track. Sometimes, it takes a week or more to get things working again - incredible job on Apple's part (sarcasm).

Anyhow, I *just* stumbled across this free "Compressor Repair" utility and had to share - I've downloaded it, and got Compressor working on my own just moments before so I've not had a chance to use it yet.

Download Compressor Repair 1.0.0 - Repair Compressor and Qmaster problems when submitting batches (http://mac.softpedia.com/get/System-Utilities/Compressor-Repair.shtml)

On the site, it says: Here are some key features of "Compressor Repair":

· Checks for missing Qmaster files.
· Checks for incorrect permissions and fixes them.
· Resets Qmaster.
· Manually launches qmasterd.
· Trashes Compressor preferences (optional).

If you do use it, let everyone know how it worked for you - good luck!

Only been two days and Compressor/QMaster failed (was only a matter of time.. it's usually a fail to work ratio of 5:1 for me) and I got to use the utility. It worked, more or less. It saved me time, and removed the cache and histories for me with ease rather than me doing the var/spool dance.

So it gets my thumbs up!