microcontroller help

dear friends, i'm using philips microcontroller P89C51RD2xx mcu to make a plc. While erasing the flash through serial communication by 'FlashMagic' software, the status bar shows 'erasing device' message and the program hangs...plz help as to what may be the problem...when i cancel the program and reconnect the mcu again by hardware resetting it into BotRom mode and then check the flash mem. contents then it is seen that the whole of the block has been replaced by 00h...i'm unable to figure out the problem. sudip