What OS version are you running? If you are running 2000.2.7SR6 or lower, it is likely that you are running into the following defect:
CSCsc17401 - OS 2000.2.7 SR6 : Callmanager crash with bugcheck 0x00000050
This crash is caused by the video driver:
Win32K.sys: 5.0.2195.7034
ATI Technology: 5.0.2184.
Are you running CSA or NIC teaming?
If using CSA:
Could you please to download the latest version from below link:
http://www.cisco.com/cgi-bin/tablebuild.pl/cmva-3des
I widely recommend you to open a case with us to find ut the root cause.
Thanks