I am unable to clear the 8th bit of data word in entire flash data memory . . .

Softwares tried:-
WinPIC800
ICProg 106A

Data given to program :-
0000 0000 0000 0000 0000 0000 0000 0000

Data read after programming:-
0100 0100 0100 0100 0100 0100 0100 0100

This is 16F628A device . . .
Another 16F628A works fine.