I use Callmanager 6.0 with Cisco2801 gw and terminate an 8-channel E1. We can receive calls from PSTN. However we can not make calls to outside ISDN cause code 44 requested/circuit/channel not available. Also the other end rings once and it stops. So people can see that who has called but the call can not be established. I upgraded the router to latest IOS. Please have a look and comment.