try making the freebsd disk primary master, since it's the one with the bootloader. if that doesn't work try GAG bootloader:
http://gag.sourceforge.net/
i've mentioned GAG in a million threads before, it's almost like i'm advertising for them. but it's been really helpful and easy to use so i highly recommend it. currently using GAG to boot my freebsd 5.2.1/win98SE system - had it all setup in just a couple minutes.