Flash Problem

We are using AT49BV322AT70TI flash chip in our design. Looks like to me the flash memory decays, meaning that after some time (uncertain) there will be some bits changed from ‘0’ to ‘1’ even Vpp is hardware pulled low to prevent any accidently writing or erasing. Is there someone else is using this flash interface to NET+50 or other processors? Let me know how it goes. Thanks in advance.

you can not just add any flash to the chip - an entry per flash type must be made the flash table and the library recompiled - use flash type already supported in the flash table