Hi,

End user has a 2921 CME with c2900-universalk9-mz.SPA.152-2.T4. User has SIP clients (3rd party VaxSIPUserAgentSDK), the issue is:

When users try to set a call many times receive an error message, when I  run a debug I see the message SIP/2.0 500 Internal Server Error

Sep 17 18:21:08.355 CDT: //380/AAA611728488/SIP/Msg/ccsipDisplayMsg:
Sent:
SIP/2.0 500 Internal Server Error
Via: SIP/2.0/UDP 192.168.15.22:5061;branch=z9hG4bK1120bf6f249d45238e17c;rport
From: "****" <sip:101@192.168.15.9:5060>;tag=920c40c6
To: "57738998" <sip:57738998@192.168.15.9:5060>;tag=6347B0-1735
Date: Tue, 17 Sep 2013 23:21:08 GMT
Call-ID: 20bf6f2-949d4-5238e17c@192.168.15.22
CSeq: 1 INVITE
Allow-Events: telephone-event
Server: Cisco-SIPGateway/IOS-15.2.2.T4
Reason: Q.850;cause=44
Content-Length: 0

What could it be the reason of this message?

how can I avoid it?

regards