When it rains it pours. A customer with a PRI is having problems making and receiving calls. They call out and get dead air. When receiving a call, the info shows up in the caller ID, but they hear nothing, and the calling party hears no ring. it is not channel specific, as one call coming in on the 3 channel won't connect, but a subsequent call from the same number to the same number on the same channel will connect.

Sounds like a co problem -- I had one a few months ago where the co was using dual cards switching back and forth (was design so if one card went out it would have a backup card). One of the cards would not let calls go out/come in all the time

update: it was a CO problem. Bad Router.