Tags, Grafts, and Clones, oh my!

Hi all-

I'm currently working on migrating my company's SVN repository to git.  Based on a conversation with Ram at the beginning of the summer, I'm using svn-fe plus a couple of my own scripts.  To create the git branches and tags from the svn-fe generated repo I clone a bunch of "mini-repos", which I subdirectory-filter, then git fetch the branches/tags from the mini-repos into a "fusion" repo where I graft everything back together, and finally one last filter-branch to permanently commit the grafts.

Unfortunately I'm running into a problem with cloning the resulting repository.  Any git tags that are not associated with a live branch are declared invalid:

   error: refs/tags/tagFoo does not point to a valid object!

I've now reproduced this issue in micro (much easier to work with than the 20k commits in the real repo), and it does go away if I git checkout -b branchFoo tagFoo before cloning the repository.  I've examined the source repository, and the tag appears valid to me, as does the commit it points to.  The first error I see is during the clone.

Does this situation make sense to anyone?  If it's a potential bug (rather than user error), I can submit my testcase.  I'm currently working with git 1.7.2.1 on MacOS 10.6.4.

Any ideas will be greatly appreciated!

Thanks, Stephen