I set up a DFS share using the documentation and it worked wonderfully with Windows XP clients, but it failed on Windows 98 clients with the error message "Folder_name is not accessible. Storage to process this request in not available."
After running log level 3 it appeared that the Windows 98 machines were making their requests in ALL CAPS and causing some sort of case sensitivity problem in msdfs.c, because it wouldn't pass a referral.
My work-around for now is to put the DFS share and DFS links in all caps, but that is really ugly and would make the XP clients suffer for 98's shortcomings.
This was the log entry from the Win98 machine that tipped me off:
[2009/07/06 07:15:54, 3] smbd/msdfs.c:get_referred_path(873)
get_referred_path: No valid referrals for path \SAIGON\DFS\PRODUCTION
[2009/07/06 07:15:54, 3] smbd/msdfs.c:setup_dfs_referral(1173)
setup_dfs_referral: Path to alternate path(s):.
^-- My server name is saigon, so this appears to be the Win98 machine requesting a referral for DFS\PRODUCTION and Samba failing. The XP clients were more well behaved.