[PIC]: Memory Map Question

All,

I have a question for the PIC community that has me stumped at the
moment.  Here is the scenario.
I am using an ispPro programmer from Basic Micro.  It works well, and we
have used it for a long time.
We have a 16F76 in one of our systems.  I erased the program memory, and
reprogrammed it with different code.
At the end of the programming cycle, I get an error that the programmer
can't verify location $4000.  
The top of the address space is $3FFF or at least I thought it was.  I
looked at the datasheet, but didn't find anything
about address $4000.  I thought it might be a system location that is
only availabe to the device programmer at program time.

Does anybody know what is significant about this location?  When I do a
read, I see location $4000 is $80.  When I erase it, it still says $80.
It should be $FF if it is truly erased I think.  If I reprogram it with
the old firmware, I still get the error.  It's like the bit is stuck
high.  It can't be
programmed low.

Anyway, if anyone has any insight, let me know.   I would appreciate it.

 

 
Thanks and Regards,