It could be that the slic isn't complete. Post a direct download link if you want to try a modded bios.
When You Encounter a Flashing Error If you are using a program for flashing on Windows which halts upon a checksum error, you want to retry with the "check the checksum" option off because the binary file has been modified and so the checksum cannot be matched. Or if your program's not got the option disablable though it's got an "officious" feature like that, you can run a DOS program instead, with a switch of ignoring checksum errors.