ISP Status problem porting code from p89C664 to P89V664

[PCBdev]

I have written a downloader that works fine on a P89C664 chip. It uses a combination of IAP in the user app portion of the p89c664 firmware and ISP commands from a pc based program. I also used Flash Magic V2.49 to write the firmware on occasion. In my porting of the FW to the NXP P89V664 I found everything to work well EXCEPT the Status Bit write to 0 to tell the chip to boot at user address 0 doesn't work. Using Flash Magic v2.49 I could burn the chip and have the status bit written properly  but if i just write the status bit using the ISP | Boot Vector and Status Bit utility it did not work. Upgrading to FlashMagic v4.24 fixed that problem.
Can someone tell me what the proper ISP command is to set the status bit to 0.
Also NXP's datasheet for the P89V664 makes no mention of the ENBOOT bit in the AUXR1 registed (B5) but this bit MUST be set to access the IAP routines. Why was it removed from the documentation?