SCCM 2007 multicast settings for HP Procurve switches

The settings I have found to work well for both 100mb and Gigabit clients are:
ApBlockSize: 2251 (8785)
TpCacheSize: 4a6 (1190)
TpExpWindowSize: 2 (2)
TpMaxWindowSize: 8 (8)
TpMulticastTTL: 10 (16)

Also if you're using HP procurve switches, change the multicast range to 239.0.1.1 to 239.0.1.254. Otherwise the HP switches won't see the traffic as multicast and your switches will flood your ports with excessive traffic.

Also ensure igmp is enabled on your switches.