I'm running horde-3.1.2, but other versions may be affected as well. I believe vapier@gentoo.org has been handling the horde ebuilds. I ran into an upstream bug when when trying to add a permission to the datatree I'd get "Invalid parent permission". The bug is identified at http://bugs.horde.org/ticket/?id=3916 and short patch is provided there. I don't know if it's gentoo policy to apply upstream patches, but if so here's one that might be good to attach.
i'm still unable to access the upstream bug tracker
Created attachment 94660 [details, diff] patch from the horde bugzilla Attaching the patch posted on the horde bugzilla. I can get to it fine from here...
*shrug* must be funky routing tables
added patch to 3.1.2-r1