if the hierarchical (complete name including O and OU (Company)) name of R8 is not identical to the R4 one, and there is reader and/or autor fields, things are going to brake.
there is other causes, but less likely.
AdminP (or Adminproxy, see Help in Administrator Client) is your friend, but I would guess you are out of luck if you are not upgrading at least to 6.5x first.
I would suggest you look for someone with expertice in the area.