[Plugin: Gengo] Invalid feed with spanish language

I want to provide feeds in the available languages (Spanish and English) of my blog. While there is no problem with the english feed, the spanish one is not valid, so I can’t add it to feedburner. Feed Validator shows this error:

XML parsing error: <unknown>:34:44: not well-formed (invalid token)

You can check it here. It seems that latin characters like ‘á’ are shown with a ‘?’. Can aynone help me please? Seems to be a problem with encoding.