Customer has an ACS R7 Processor with Large PC Card. Callers to one extension get a "Mailbox is Full" reply when they try to leave a voicemail for the extension, but the mailbox is empty and the light isn't on. I initialized the mailbox to wipe everything out, and verified that the mailbox is in "Record" mode, but testing it we still get the "Mailbox is Full" message. What else could be wrong?