Until recently I had a HPUX 11.23 IA64 Master server and a handful of 11.23 IA64 media servers. running NB 6.5.4.
So yes supporting Itaniums. They keep adding support for OS's on IA64. eg SLES 11 was just added
But always check in here with the latest OS Compatibility matrix (Jan 2010) for NB 6.x and might as well review for NB 7.0 also at this URL
http://seer.entsupport.symantec.com/docs/325328.htm
Just check the Operating System and it will tell you if it supports the OS on IA64 as Master, Media Server and/or Client. Some may only support Client at the least. ie OpenVMS