Are you seeing that Error code in the Mediant logs or the CIC logs? There is no ISDN or SIP cause code of 304 so I would be curious to see where you get this message. What version of CIC are you on including SU level, What HMP version and SU are you on, and what firmware is the Mediant 2000 on? If you look at the TSServer logs and SIP engine logs on the CIC server do you see anything that could help explain what is going on. You may also want to look at the Mediant logs to see if it can explain what is going on.