flash error problem.

Hello.

we are working with M29W160ET Nor flash and sometimes contents of some part of the flash is changed. This seems to happen when device is turned on/off and 0~0x40 or

0x100~0x140 or so is changed. We think this is maybe due to electric shock or static electricity but if anyone experienced this kind of thing please tell me your experience or solution, if any

Thanks.