I *think* this is the only post that mentions a Tiger server actually working, as opposed to supposedly working? Can't get it to work here for a 10.4.9 Mac serving a 10.6.2 client. I have SharePoints on the Tiger Mac; even sharing the desired network drive as SMB still shows it connected and mounted via AFP when viewed from the 10.6 client. I have no clue what's going on there but will look into that more.
TM fails trying to "make available" or "preparing" the network disk with an error regarding a −1 copy of the network share. The .tmp sparsebundle mentioned before is also made during this process and then deletes. Before and after, adding the .plist file with UUID as shown in System Profiler produces the same result.
OK, resolved the issue of the network drive mounting with AFP; I had been connecting via a Finder window instead of Cmd-K and entering the smb:// IP address.
Otherwise I still have the same issue as mentioned above.