Invalid response from server when used on a og post

If the content type is able to posted into an organic group, using hs to select taxonomy produces "Received an invalid response from the server."

With an og post add of http://../node/ognodeadd?type=notice&gids[]=263 I see in the debug console
POST http://..../hierarchical_select_json?type=notice&gids[0]=263 500 internal server error

If I use the same taxonomy selection on content that does not post into a group such as
http://.../add/page i get POST http:// ..../hierarchical_select_jason and all works ok.

DP 6.19, OG 2.1