I'm having the same problem with that provider, Lluis. It seems that Mapserver includes the parameter "EXCEPTIONS=application/vnd.ogc.se_inimage" at the end of the request, and the provider doesn't like that parameter.
I have searched the documentation but I haven't found a way to change the way Mapserver generates the actual requests to the wms servers. I think that a possible solution would be to make the connection to the wms provider trhough a HTTP proxy. Then you could make the proxy filter out the "EXCEPTIONS" parameter from the HTTP requests. Incidentaly, caching the requests to the wms provider in an HTTP proxy seems a good idea too, doesn't it? Have you found any other solution? Greetings, Xavier Pereta
