First, I made a backup of my /dev/sda partition table with the command: sfdisk -d /dev/sda > sda.out
That way, I can restore it to previous settings with the command:
sfdisk /dev/sda < sda.out
Then, I ran your command:
sfdisk /dev/sda << EOF
It works with this output...
Device Boot Start End #cyls #blocks Id System
/dev/sda1 0+ 12187 12188- 97900109+ 83 Linux
/dev/sda2 0 - 0 0 0 Empty
/dev/sda3 0 - 0 0 0 Empty
/dev/sda4 0 - 0 0 0 Empty
So anyway, that command does work on my FC5 box, don't know why it's not working for you.
sfdisk (util-linux 2.13-pre7