I'm quite sure this is related to the fix for another issue ("Unable to show log of a deleted branch", see [1], code changed in r29682) and it only occur when you don't have R access to the repository root but only to a subfolder.
Workaround is probably to make sure you have R access to the repository root, but that may be undesirable.
I will try to think about a possible solution.
Kind regards,
Daniel