QMaster is obsolete.
Two things to try:
1- Launch Compressor, go to Preferences, to Advanced, click the "Reset Queue" button.
2- Select "Cancel jobs" and click "Reset"
3- Click the "Reset Queue" button again, this time select "Repair Compressor", click the "Reset" button.
If that doesn't work, dowload the free app "FCS Remover" from DigitalRebellion (dot com). Use it to totally remove Compressor from your system. Reinstall. Simply moving the app to the trash leaves tons of system files scattered all over. FCS Remover will gather up every single related file and remove it for you quickly, easily, safely.