og_context segfaults

I recently upgraded OG from 7.x-2.0 to 7.x-2.1 and discovered that node/add stopped working; browsers displayed ERR_EMPTY_RESPONSE and Apache logged:-

child pid 20892 exit signal Segmentation fault (11)

-: to its main error log. Nothing was written to the vhost-specific log. stracing Apache didn't immediately show me anything interesting.

Relevant env data:-

[root@xxxx ~]# httpd -v
Server version: Apache/2.2.23 (Unix)
Server built: Jan 29 2013 12:37:17
[root@xxxx ~]# php -v
PHP 5.4.13 (cli) (built: Mar 14 2013 09:53:35)
Copyright (c) 1997-2013 The PHP Group
Zend Engine v2.4.0, Copyright (c) 1998-2013 Zend Technologies

Disabling og-context resolves the issue, but this is obviously less than ideal. Any thoughts? Anyone else had this?