I found out (at least on one forums I host), that if I (the first user) disables PM's for myself, it disables them globally. I can't go into the main preferences and enable it (even thought it shows up as disabled). If I re-enable PM's on my account, it enables them globally for everyone.

So either this is just a bug with one of my forums or we have no takers  :(

I don't see anywhere that it can be disabled in the Member Panel !

It's on the admin manager section in the member control panel, where you click "Disable Private Messaging - Check this to disable Private Messaging for only this user."

oops, missed that but doesn't happen on my test board.
Disabled for me as admin and 3 test accounts are still enabled.

I recently turned over forum control to someone and I disabled my PM's but it disabled them for everyone.

Never seen this before.
When you disable PM's it adds this to the individuals .dat

pmdisable = |1|

I knew that part but I just wouldn't know why it did what it did.

When I disabled my own PM's, it changed the setting globally (meaning it also showed up as being changed in the main board preferences section on the admin panel).

I've tried it several times now on my test site and can't recreate the problem.
Maybe the new site manager disabled PM's globally ?

He actually doesn't know how to do them (which was mighty weird to make him the admin but that is the way the ranks go). It updated every time I disabled and re-enabled them on my account, but I couldn't change it in the admin panel even though it showed them as being disabled.

Then I can only advise that one of the files are corrupt.
Have you installed any mods?

Nope. I even reinstalled the board and got the same issue.