XSLT in Mozilla 3.5.7

Hi Guys,

I'm stuck doing a XSLT-Transformation using FireFox.
All I'm trying to do is to AJAX a xslt and xml and save the resulting
code in a variable.
The xslt is kind of a code generator for a workflow-execution-engine
we are working on, thats why it generates plain text.
The confusing thing is, that xmllint and xsltproc don't find any
errors and epiphany also works it out right.
But Firefox always come up with the following error:

Error during XSL transformation:
[Exception... "Component returned failure code: 0x80600001
[nsIXSLTProcessor.importStylesheet]"  nsresult: "0x80600001
(<unknown>)"  location: "JS frame :: http://www.pri.univie.ac.at/~ralph/xslt-test.html
:: anonymous :: line 40"  data: no]

I've no idea what FireFox is trying to tell with this. Using FireBug
shows me that this error is thrown at importStylsheet() what bring up
the assumption that the xsl is wrong, but I cant figure out where or
what.

Link to xml: http://www.pri.univie.ac.at/~ralph/workflow.xml
Link to xsl: http://www.pri.univie.ac.at/~ralph/wee.xsl
Link to page: http://www.pri.univie.ac.at/~ralph/xslt-test.html
(includes only sniplets of the original javascript - but works for
testing)

If anyone of you would have a solution or even a smart advise it would
be great.

Cheers,
  Ralph