This usually happens when there is only a few minutes left of the recording, and I think it's related to saving the bookmark in the recording, as I get entries like this in the mythbackend log:
Sep 23 18:57:43 mediabox mythbackend: mythbackend: E ProcessRequest mainserver.cpp:784 (ProcessRequestWork) Bad SET_BOOKMARK
I also found this in the MythTV 0.27 release notes (http://www.mythtv.org/wiki/Release_Notes_-_0.27):
[a8722fa] Correct sanity check on SET_BOOKMARK protocol command Fixes #11104
Forgot to mention: using the 1.6.11 version of xbmc-pvr-addons (from https://github.com/fetzerch/xbmc-pvr-addons.git), frodo branch.
Is the frodo branch being updated, or am I out of luck?