like that in link above:
label ws1
MENU LABEL WS1
kernel /nfs/ws1/bzImage
append initrd=/nfs/ws1/tinycore.gz nfsmount=192.168.1.3:/tftpboot/nfs/ws1 tcplist=192.168.1.3:/nfs/ws1/nfs.list tce=nfs/tce
bzImage and tinycore.gz are in /nfs/ws1/ and also in /tftpboot.
When i change "default" to your version i have the same resultat ;/ my tftpd doesn't share that file