Most CB auditor's I have dealt with don't care about open CA/PA's
as long as there is documented progress.
The third section on all of our CA/PA's (basic info and description are one and two) we have a place for "root cause". This is expected to be determined before any action is taken. From Root Cause, we might decide if it requires a 6-Sigma action, it would then get turned over to one of our green-belts with the manager being part of the team.
One of our Management Review items regarding CA/PA's is "open over 30-days". In MR, each OPEN action is discussed as to it's current status, what's been done, what about this, why not, etc. As Management Rep, it is my job to know the status before going in. I am not the one who controls CA/PA's, (that is our QC manager), but I do pester the person they are assigned to for periodic updates. If I need to, I CC the plant director on my status request e-mails.

In six months, IMHO some "progress" should have been made, if even gathering evidence for his root-cause analysis. Check in and see what the assigned manager's reason is for not handling it, aside from "being too busy"? Can he delegate this task to one of his people? Does he not know where/how to start the process?
From this discussion, you could then determine if a new CA is warranted under one of the many clauses others have suggested.
