I`m experiencing the same problem as Arty here, but I will test this when i get home. I used the sidechaincompressor plugin, which has it`s own bus-es and stuff. but it wasnt working very good.
I to use the sidechain compressor that came with cubase 5, and enabled sidechaining on the channel, but could only get one channel through it. I tried adding more channels to use the same sidechaining "bus" but the other channels didnt output anything.
Probably just a rookie mistake, but I got sick of it and went out for a beer instead
