Mergetool generating blank files (1.5.3)

At work, I've been using a git-svn import for my daily workflow (still
somewhat of a git newbie, but now has come to the point where it's
tough to work without it), and while rebasing from svn (on a rather
old branch), I found that the mergetool option does not work too well
for me.

I am using version 1.5.3 and I have tried all of the different diff
tools (save opendiff) that are supported by git -- but in the middle
of a rebase, whenever I run the mergetool, the LOCAL, REMOTE, and BASE
temporary files that are created are all empty.  The BACKUP file
remains, and still has the proper 3-way-merge conflict syntax (with
<<<< ==== >>>>) and such, but the other files are all empty -- and
thus the mergetool of choice does not read it (it shows up empty there
too, of course).

What could I do to fix this?  I'm confident that there are conflicts
(git tells me so, and I end up manually going through all the files in
emacs anyways, but it's very tedious); or is there another tool that
reads the 3-way-merge syntax (the < = >'s) and lets me pick one or the
other, or do I have to write my own?

I know there's just something funky on my system, because someone else
doesn't seem to have this problem on his computer -- maybe it is
because I use the svn rebase, but it does that when I rebase onto
another branch too.

Thanks.

-- 
Kelvie