[U-Boot] can't update U-boot when booting with BDI2000

[hendrik]

Hi

Im new to U-boot and need help. I am using U-boot-2009.10 and a MPC8548 
board with 512MB DDR and 128Mb nor Flash(using cfi)

I am booting the board using a BDI2000 by loading my u-boot.bin file to 
the bootregion in my memory map (FFF80000) and running from the reset 
vector. Uboot starts up and works fine. I am able to unprotected the 
flash ( confirmed with flinfo) and can erase sectors other than the 
bootsector.  I have placed the output below.

UBoot=> protect off all
Un-Protect Flash Bank # 1
UBoot=> erase fff80000 ffffffff
.. done
Erased 2 sectors
UBoot=>

When I look at the erased memory using md the u-boot image that was 
loaded into memory by the bdi is shown at the bootsector address fff80000
UBoot=> md fff80000
fff80000: 00300030 552d426f 6f742032 3030392e    .0.0U-Boot 2009.
fff80010: 30312d30 30323236 2d673663 36653034    01-00226-g6c6e04

if i reboot the board not using the BDI the bootregion shows the old 
uboot image and was not erased.

I think the sram is mapped over the flash boot region and when i try to 
erase and cp to the bootreagion the commands and date gets lost.  Can 
anyone help me find the problem?
thanks Hendrik