soon as I disable the plugin, everything is back to normal. The post *does* get edited, but no emails are received by any subscribers. Tried installing the Error Reporting plugin (http://wordpress.org/extend/plugins/error-reporting/) but it didn't seem to record any error..
centos 5. wordpress 2.9.2
> php -v
PHP 5.2.11 (cli) (built: Sep 21 2009 14:52:42)
Copyright (c) 1997-2009 The PHP Group
Zend Engine v2.2.0, Copyright (c) 1998-2009 Zend Technologies