I was running DSB's Bamf Cubed 1.0.2, when I decided to try out an ICS Rom. But I had a problem...every rom would flash and boot into the bootloader but fail to flash the kernel and give me the following error...
"Main Version is Older!
Press <POWER> to reboot"
Then I have to pull the battery and remove the SD card to remove the PH98IMG file before reflashing the old rom.
I have learned this is an issue with the Kernel DSB made being based off of a more recent base than the one in the ICS ROMs. There are several methods around this....but I think this is the easiest (since when the kernel update fails you cannot use fastboot until you remove the PH98IMG file from you SD card using your PC or another method other than your phone)....
After you download your preferred ICS rom, use a program like 7zip to explore the zip. locate the boot.img in the kernel folder and copy it into the folder on your pc where you have your fastboot.exe. Then put the zip for the rom on your ext_sd and you are ready.
Boot to bootloader
open command prompt and cd the folder fastboot is in
"fastboot flash boot boot.img"
Then reboot straight into recovery from the bootloader and flash the ROM. When it is done it will try and flash the kernel again and fail...but don't worry. you are good already. you will boot up with no problem.
edit: link to a guide on fixing this in post 5