xincludes with Xerces 2.6.2

Guys,

I'm having a problem with xincludes. 

The tool chain: Saxon 6.5.1 with Xerces 2.6.2.

I'm including the same file in two different documents - the included
file is a "section", and it gets included in "article" files. However,
when processing one of the articles I get this error:

"Error reported by XML parser: The prefix "xi" for element "xi:include"
is not bound."

The other article parsed just fine.

Xerces is complaining about a nested xinclude in the section file. Now,
the interesting thing is that it seems to depend on where in the
document I include the section. If I include the section after just some
intro <para> stuff, everything is ok. But if I do the inclusion inside a
section in order for the included section to be nested, the error pops
up.

Anyone experienced anything similar?

/claus