I'm also having trouble getting a 10.4.3 1099 dual boot system running. I did the following:
Partitioned a Windows NTFS volume, and a HFS+ (Type AF) volume. Then I ran the Mac OS X DVD Install, which after rebooting with the DVD In the drive booted up the hard-disk version of OSX fine. After the second reboot, nothing would load at all. So I reinstalled XP on its drive, which allowed the system to boot to XP. I then tried the chain0 trick, but that resulted in going back to the BOOT.INI bootup menu. I tried dd'ing the first 512 bytes of the OSX partition and running that from BOOT.INI - this resulted in the dreaded "HFS+ Partition Error" problem. Presently that partition is set to type AF, and the XP partition is bootable. They're both primary volumes.
Here's the fun thing - If I boot from the DVD, and make the installed OSX partition the Startup Disk, the partition boots fine, however then I can't boot to XP unless I fdisk the XP partition back to the bootable partition.
Any advice on where to go from here?