navaho, this can be very insightful. I did have some corruption in the pm_users directory... had complaints of PMs in users inboxes that didn't belong to them and incorrect pm counts. The problem was fixed by deleting the improper PMs from their pm_users file. I never figured this to be related to my problem(s) though. Even accounts that have no PMs show the nfx.... and the big reduction in cache % leads me to believe everyone is having this issue.
This could be off topic, but while we're here.... can someone explain Cookie_Number? I see it in the vars config and in the pm_users files.