'Illegal argument exception" in Xalan Transform

[Brian Dobby]

Hi. I have just updated the version of FOP used by a servlet running
under Tomcat to 0.20.5 (previous version unknown). I included all
FOP's support jars, including Xalan. Now a Xalan transform in the same
servlet fails with:

The output format must have a
'{http://xml.apache.org/xslt}content-handler' property!

Can anyone tell me what's going on? I know little about the Apache XML
products, so it may be something really simple. I did the upgrade to
ensure a consistent FOP environment for the servlet, which previously
had a version of Batik incompatible with it's version of FOP.
TIA
Brian