Possible bug in json_encode() in default_transcoder.php

I have been doing a simple select from mysql and insert into couchbase, and i dont have any errors in my code, but I get this warning on every document insert.
json_encode(): Invalid UTF-8 sequence in argument in [CouchbaseNative]/default_transcoder.php on line 80

Has anyone come across this before?

Thanks

Nick

Not a PHP guy but it seems this has happen to other people as well: http://stackoverflow.com/questions/10205722/json-encode-invalid-utf-8-sequence-in-argument

Have you try this option: mysql_set_charset(‘utf8’);

i had not, i shall give it a go,thank you, character encoding is definitely one of my weaker areas.