When using a slipstreamed CD, during the text part of the installation I get an error "Cannot copy file X" (I don't remember the exact error). I can press Enter to try again, F3 to abort, or Esc to skip that file. This only happens when I slipstrem hotfixes, not when I ss only SP2, and it happens with nLite, RyanVM and HFSlip. There are usally about 3-7 files like this, but they seem to be random (it's not always the same files).

Can somone suggest any workaround (maybe a manual slipstram? *shudder*)

I doubt the error is with your method of slipstream. Since the files varies each time, my guess is a bad CD ROM. Try switching the CD ROM and see if the error persists.