Microcontroller reset pin is always in HIGH state

I use 89C51ED2 (44 pin PLCC) in my circuit and I am facing a peculiar problem. The reset circuit of micro-controller consists of 8.2K and 10uF capacitor. When powered on the reset pin (PIN 10) remains in HIGH state, even though it is pulled down to ground by 8.2K resistor. I checked that RESET pin is not shorted to VCC. This problem persists only in a few PCBs and rest of the PCBs works fine. I have used identical components in all PCBs. But when I remove the micro controller, PIN 10 of IC base comes to LOW state. What can be the reason for this problem? Thanks in advance.