One of our remote offices (also on a 5600) keeps getting "ARS is busy" when trying to get an outside line and a reboot of the system is the only fix.

They only have 4 pots lines at this location.
(Connected to the main office over a VPN as well)

It's a small office and nobody else is on the phone when they have gotten this message.

Anyone have any thoughts.
I've double checked the configuration and everything seams to be ok.
Could I be missing something?