wallaby 6.22 cannot be downgraded to 5.15

[andhy]

I have my xda fixed by O2 with a new bootloader 6.22. I tried to downgrade to 5.15 without any success. I did downgrade my 5.17 to 5.15 without any problem, but cant repeat it for the 6.22.
Can anyone please help?

[itsme]

are you using 'pnewbootloader' to do this?

it only works for a limited nr of rom versions.

what rom version do you have?

[andhy]

ROM version 3.20.06ENG dated 07/30/03
I used the bootloaderfix batch file withuot any success, then
I wrote the 5.17 patch to SD also did not work, then
I wrote the 5.15 ROM image to the SD using XDArit10 also no success

[andhy]

I put the xda on the cradle connected to the PC thru USB and tried to run the pnewbootloader, without any luck. Nothing happened

[andhy]

my objective is actually to upgrade the O2 ROM to ATT WM2003. But I dont want to upgrade the radio stack. Suppose it is impossible to trick the wallaby 6.22 to accept the SD. How about running the ATT WM2003 upgrade, but removing the RSU upgrade application program in order to 'stop' the rsu upgrade from running. Will this work?
THanks a lot for your help...