checksum error

I recently attempted to upgrade bios program on a Matsonic MS6261 MB and now have a paperweight. On re-boot, received “checksum error” message following a “Bootblock BIOS Ver xx” and if I have a boot disk in the A drive, it will boot to it, but bypasses POST altogether, making it impossible to enter BIOS setup. Any suggestions??

5481@bellsouth.net (my alias has the wrong email and unable to update)