Access OS X Server file share from Ubuntu

I've been struggling with this for a while and I'm hoping somebody here has an answer. I have a Mac OS Server with file sharing tued on and everything as wide open as I can make it (777 permissions, guest access allowed, all protocols open). I can see the server from my ubuntu installation and when I click on it I'm asked for a useame and password but there is no combination (valid user on either machine, empty useame and password, admin accounts, default useame and password, random junk) that lets me access the share. Other macs have no issues accessing it and, weirdly, multiple Windows 2000 computers have no issues accessing this share.

I've searched and searched and tried every configuration I can find but I can't figure out how to access this share from my ubuntu machine. Any ideas?