Voicemail delayed to extensions

Situation: Customer calls and leaves voice mail at 11:00 AM. User checks voice mail at 1:00 and 3:00 PM, no messages. User checks voice mail at 4:00 PM and voice mail message is there.

We are running Asterisk 1.4 on OS Centos5. This is a Fonality PBXtra build. The extension is a virtual extension in a call queue. No other users are complaining of this. I have checked the file names on previous instances of this happening and date/time stamps indicate time customer left message, but it showed up in voice mail system some hours later. It is not always the same amount of time delayed. Some messages show up almost instantly.