I've run into a mysterious error that I seem to be unable to track down.

(Location of error unknown)XSLT Error (java.lang.InternalError): fillbuf

I'm running Xalan Java 2.2.D11.

Does anyone have an idea of where I might look? Thanks!

I'd first try to upgrade to a more recent Xalan release. If this
doesn't solve the problem, search Apache Bugzilla and/or subscribe
to the Xalan user list and ask there.
The XSL list is not the most appropriate list to ask this kind of
processor specific questions.