I have recently added this mod and got it working with the disable new data permissions and changing the connect url but lastnight whenever i added a product all i was getting was a blank page and no update to facebook. I ran the debug error logging utility and it pointed to this mod.

Code:
[26-May-2010 13:01:33] PHP Warning:  json_encode() [<a href='function.json-encode'>function.json-encode</a>]: Invalid UTF-8 sequence in argument in /data/www/vhosts/gadg3tshop.co.uk/httpdocs/admin/includes/modules/update_product.php on line 168
[26-May-2010 13:01:35] PHP Fatal error:  Uncaught exception 'FacebookRestClientException' with message 'Session key invalid or no longer valid' in /data/www/vhosts/gadg3tshop.co.uk/httpdocs/admin/includes/modules/facebook/php/facebookapi_php5_restlib.php:3374
Stack trace:
#0 /data/www/vhosts/gadg3tshop.co.uk/httpdocs/admin/includes/modules/facebook/php/facebookapi_php5_restlib.php(932): FacebookRestClient->call_method('facebook.stream...', Array)
#1 /data/www/vhosts/gadg3tshop.co.uk/httpdocs/admin/includes/modules/update_product.php(170): FacebookRestClient->stream_publish('New Product!', '{"name":"Red an...', '[{"text":"Gadg3...')
#2 /data/www/vhosts/gadg3tshop.co.uk/httpdocs/admin/product.php(62): require('/data/www/vhost...')
#3 {main}
  thrown in /data/www/vhosts/gadg3tshop.co.uk/httpdocs/admin/includes/modules/facebook/php/facebookapi_php5_restlib.php on line 3374
I looked at the settings and now my connect url has changed and it says you cannot point to a facebook domain.

Any ideas?