Hey, I dont know what the problem could be, but whenever, i install a linux distro, the distro will usually configure the bootloader automatically, after asking which loader to use and which drive to put the loader. I Personally use lilo, ive never used grub. If you want lilo to be the bootloader, then select hda to install the bootloader to your MBR on that partition. You can use the 2k loader. Just download, a tiny program called bootpart, and run it from terminal in 2k, it will list all partitions and tell you what partition linux is on. Oh yeah if you use this method, then you'll need to note the linux partition letter number combo when you set up partitions eg. hda7 or hda3 ect. that way the linux loader will be installed to the linux partition instead of the 2k partition. After you run bootpart and figure what number the linux partition is you just type : bootpart 7(#of partition) Linux(whatever u want to show up in the 2k loader) linux.bin this will create a file called linux.bin, and add the necessary info to boot.ini. for more detailed info do a search for bootpart, or go to www.tweak3d.net
they have some excellent guides on dual and triple booting. Worked great for me with both Mandrake 9.0 and Redhat 8.0. Im still a newb myself, but ive never had any problems dual or triple booting.