SiRPACs reaction on '&'

Hello,
I'm experimenting with SiRPAC. It seems, that SiRPAC doesn't allow the
'&'-symbol in any context of an RDF-document. I even get an
error-message (the
messages are always different and not very expressive) when I place the
symbol in the value of a comment-property. Can anybody tell me why?

Thanks, C. Capelle