Unfortunatly, it's not a problem with the unit.
I've got two HiMD recorders (a RH1 and a NH1) and the disc is played with the same issue (AccessErr) at the same point in the recording.
Th recrding has been made with the RH1 and since I've recorded that live I've done other recordings without any problem with this unit.
It's not a HiMD 1Gb disc though, it's a 80min MD.