Aladdin Advance won't flash!

[sevi]

Hi all, I installed an Aladdin Advance chip in my friends xbox and have been having a few problems with it. I have done a few Aladdin installs and this is the first one that has given me grief. About a month after the install my friend was complaining that the xbox was freezing up during some games (I also did a hdd upgrade) he was playing off the hdd. When he returned the box I tried booting up and found that it wouldn't always boot properly with the chip enabled ie. wouldn't flash red, amber then green when the power button was held down.
I checked my solder joins (straight solder to mb, no pin header) and found one was a little dodgy and the joint for the d0 point on the mb was a little loose. I fixed them and all seemed to be good. But a few weeks later he said he was having trouble again. I am now in the process of fixing it and I thought it might be a heat problem. I just used xbtool to hack a version of the x2 4981.06 bios and increased the fan speed from 25% to 65%. I transfered the new bios.bin file to the c:\bios folder on his hdd and tried to reflash this bios. I held the power button in for three seconds and the power led went red then flashed amber a few times then turned green and the evox dashboard booted up. When i tried to flash the bios it said "Flash not Writeable".
Is the chip screwed or am I doing something wrong?
Any help would be greatly appreciated.
Cheers.
P.S. Sorry for the long post.