Rick:
in this thread I posted a suggested circuit for AT89S8253:
http://www.8052.com/forum/read.phtml?id=132901
The AT89S8252 dos not show power up problem, so you could use the /POWER_OK part only.
The idea is checking /POWER_OK low before starting any EEPROM writing cycle. The 1000uF cap. should give time enought to finish the cycle.
This is some possible code for writing one byte a time:

  void write_EEPROM(unsigned char dato,unsigned char xdata *add){
      if(_POWER_OK==FALSE){
         WMCON=WMCON|EEMWE_; // EEMWE high
	 ET2=FALSE; // stop interrupts
         *add=dato;  // start writing
	 while((WMCON&WDTRST_)==0); // wait WDTRST=1 (2.5ms)
	 ET2=TRUE;  // restart interrupts
	 WMCON=WMCON&(~EEMWE_); // EEMWE low
      }
  }

Disabling interrupts is important: if an ISR tries to read EEPROM while being written (even a different address) the result is wrong. So, disable interrupts before writing, unless the ISR does not use EEPROM at all.
Although I do not have reset problems (and I use simple RC) it is a good idea to use a dedicated reset chip.
Daniel