After considerable wasted effort, I think I have finally
figured out the main culprit thwarting my attempts to get
multiple OSes including Plan 9 installed on a single disk.
Apparently the 10MB "x86 boot" partition that Solaris 8
really wants to use messes up something in the partition
table and possibly in boot blocks in other partitions.
Anyway, when I forced an installation without the x86
boot partition, all four OSes (WinMe, Win2K Pro, Plan9r3,
Solaris8) ended up being bootable and useable. (I'm using
System Commander to handle the various multiboot tasks.)
Anybody else having similar problems might try this.