Attachment Permissions Problem

[s0lidgr0und]

I've been an admin for three years and I'm embarrassed to admit that I can't figure this problem out.

Out of nowhere, nobody on my board can post attachments, even the admins. I looked through all of the settings and everything looks good.

In vBulletin Options > Message Attachment Options:
Limit Space Taken Up By Attachments (Total): 0
Attachments Per Post: 250
Attachment Upload Inputs: 10
Attachment URL Inputs: 10

In each usergroup, the attachment options are:
Can Upload Attachments: Yes
Space (in bytes) that a user's total attachment usage may consume: 0 (Unlimited)

What am I doing wrong?