I had this problem the first time I installed Boot Camp, back when it was first released. First, perhaps obviously, make sure you have the latest firmware. Then, insert your Tiger Install Disk 1, quit the install, and I think it's under Utilities, open Disk Utility. Repair disk.
That solved the problem for me, so many months ago. Hopefully it will help you, too.
EDIT: Okay, I guess I didn't read the warning close enough. Because OSX didn't tell me I had multiple volumes on the drive. Maybe repairing the disk would still be worth it though, before having to back up and reformat the whole drive?