A customer is experiencing intermitent calls that instead of getting routed to an agent or queue (if agent isn't available) are getting the system message below when users dials (for example 1 for marketing). This happens on about one of every 15 calls and happens when their are only two or three calls going through the IVR. Any ideas of what could cause this?

I'm sorry we are currently experiencing system problems and are unable to process your call. Please call back.

Again, this happens on about one of every 15 calls and load on IPCC X is very low.

thanks in advance,