xsltproc and XML catalog

I am having a problem specifying the XML catalogs for xsltproc in Cygwin:

XML_CATALOG_FILES="file://c:/mydoc/docbook/catalog.xml 
file://c:/usr/share/docbook-xml42/catalog.xml" \
XML_DEBUG_CATALOG=1 \
        xsltproc --xinclude --stringparam html.stylesheet "help.css" \
        c:/mydoc/docbook/test.xsl test.xml
Resolve: pubID -//mycompany//DTD DocBook XML V4.2-Based Extension V1.0//EN
268632096 Parsing catalog c:/mydoc/docbook/catalog.xml
c:/mydoc/docbook/catalog.xml added to file hash
Found system match abinitio-docbook.dtd
Resolve URI file://c:/mydoc/docbook/abinitio-docbookx.dtd
file:///c%3A/cygwin/usr/share/docbook-xml42/catalog.xml not found in file 
hash   *** NOTE the '%3A' following 'file:///c' ***
  <Failed to parse catalog 
file:///c%3A/cygwin/usr/share/docbook-xml42/catalog.xml
/cygdrive/c/cygwin/usr/share/docbook-xml42/catalog.xml not found in file 
hash

The colon (:) following the drive letter is mangled to '%3A', and xsltproc 
cannot locate the second catalog entry.
Anybody know what's going on?

-Taro

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