This all works for me. I am currently using Mozilla 0.9.9, with the latest version of Hijack -- includes some fixes for the latest Mozilla.

I still find it necessary to use the script, though, so for the benefit of all I have attached my current "/usr/local/bin/xmms" script to this posting. To use it, just ensure that the script gets run by mozilla instead of the real xmms binary.. it's a $PATH thing.

Cheers