Note: this bug is solved with the latest 5.10 patch.
In order to resolve an issue where a ColorProof job is stuck in a nesting state, cannot be deleted and holds up all other jobs from printing, please follow the instructions below.
To avoid the error, when deleting jobs please first right-click and choose 'Cancel'. Then wait a few moments for the job to show Cancelled status, before deleting. Do not try to delete the job whilst the cancellation is 'in progress'.
First, and most importantly, create an environment backup under System > Environment Backup > Create.
After a successful backup, shut down ColorProof and its services. The services can be closed by right-clicking the ColorProof icon located in the taskbar/notification area, and choosing Shutdown.
Please note that the following steps will clear your job queue and history. After relaunching ColorProof, any image files (PDFs, tiffs) still inside your hotfolders will be reprocessed. You may wish to clear out your hotfolders of old files to prevent old jobs being reprocessed.
Next, navigate to C:\Program Files\GMG\ColorProof05 and double-click the shortcut in this folder named DbSetup.exe.
Go to 'Service Functions' at the top left of the window and choose 'Delete All Jobs'.
Close the DbSetup application.