Xalan-J 2.6 cannot find my catalog

I'm trying to use a catalog to resolve a public identifier in my DITA
DOCTYPE (PUBLIC "-//IBM//DTD DITA Composite//EN"). My CLASSPATH points
to my resolver.jar file and to my CatalogManager.properties file,
which contains the following lines:

catalogs=../catalog-dita.xml
relative-catalogs=no
prefer=public
static-catalog=yes

The "catalogs" property points to my catalog file. And finally
(whew!), this file references my DITA DTD:

<public publicId="-//IBM//DTD DITA Composite//EN"
uri="C:/DITA-OT1.3/dtd/dita132/ditabase.dtd"></public>

When I try to transform my XML doc with some basic XSL, Xalan replies
with an error: "java.io.FileNotFoundException: C:\sabadoc\ditabase.dtd
(The system cannot find
the file specified)."

On a different machine, this setup works correctly. As far as I can
tell, the only difference between the two machines is that the Sun
1.4.2 JDK on the successful machine contains a \jre\lib\endorsed
folder, which includes Xalan.jar, among other files. Could this be the
cause of the error?  I've tried to install different versions of the
Sun JDK on my unsuccessful machine (removing all prior versions before
each new installation), but don't get an "endorsed" folder.

Thanks,
Mark

Mark Peters
Senior Technical Writer
Saba Software