The webservice fails if an artist query includes an ampersand (encoded as %26). This worked correctly before NGS went live.

e.g,

> curl --dump-header - 'http://musicbrainz.org/ws/1/artist/?type=xml&name=Belle+%26+Sebastian'
HTTP/1.1 200
Date: Mon, 23 May 2011 19:35:35 GMT
Content-Type: application/xml; charset=utf-8
Transfer-Encoding: chunked
Connection: keep-alive
Keep-Alive: timeout=20
Server: nginx/0.7.65

(no body is returned)