Edgar, a while ago I got Nymonyx 65nm P30 chips as a replacement for older Strata chips. One problem I encountered is an incompatibility to its predecessors: The buffer size for programmed operations has increased to 512 words (that's not yet incompatible). However you can only use the full buffer size if it is naturally aligned.
The datasheet reads "The maximum buffer size would be 256-word if the misaligned address range is crossing a 512-word boundary during programming." Maybe this is the source of your troubles. It definitly took me a while to find this piece of information. I had suggested a patch for this issue a while back (Mar 5/6 2009) on this list. I didn't check/follow up on it to see if it ever made it to the repository. I recall vaguely that someone else contributed another patch in this area sometime later. Maybe that patch addresses the issue above as well. Best, Kurt
