Cannot Boot into GRUB2 (Madriva) Grub Error 2

[rambutan]

GNU/Grub is launching GRUB2 and calling existing GRUB Grub-legacy. Mandriva is on the bleeding edge with 2008 Spring.
I installed Mandriva (got Grub2) then I used set-up to get back to my usual menu.lst etc only to find Mandriva is locked out behind a Grub Error2. Seems the new grub does not have stage 1.5 grub-legacy refuses to boot the OS without it.
The obvious answer is to put Mandriva on a Grub-legacy diet.
Here is what worked on two PCs.
Boot my old Linux, empty a partition (call it Mandriva.new) and mount it.
cp -a /Mandriva.old/* /Mandriva.new/
delete /Mandriva.new/boot/grub
copy /MyoldOS/boot/grub to /Mandriva.new/boot
Add the stanza to menu.lst and it boots Mandriva via grub-legacy.
Here is my puzzle.
If I just copy /MyoldOS/boot/grub to /Mandira.old/boot it will not boot! I still get Error 2.
When I run grub-install to /Mandriva.old/boot I get a
"file /Mandriva.old/boot/grub/stage1 not read correctly"
and it still will not boot. It only works after a "cp -a" into a new partition!?!
Anyone know the answer to the puzzle?

Two more clues.
1. I see bug reports talking about inode sizes. I don't know what they're talking about. Could it be that "cp -a" drops the new larger inode size down to the older size and all is well?
2. I saw one person saying they solved it with chainloading like for Windows.