I am trying to do the following:
document('file:///c:/servers/mserver/ojamc2vpt1_part.xsd') to open a
document not in the same directory as my stylesheet. It does not work.

What actually is "not work"? Do you get an error,
or does the style sheet produce an unexpected
(probably empty) result?

For a starter, use a good command line processor like
Saxon to check. It will give you a proper error message
if the file couldn't be accessed or contains syntax
errors or a DTD which could not be accessed.
If there is no problem with access, make a simple file
containing
 <xsl:value-of select="name(document('...')/*)"/>
This should result in the name of the document element
of the file put in the output, otherwise something fishy
is going on or you missed an error message. After you've
verified the file is properly read, check what you do
with the result of the document() call, for example you
might have misspelled the match in the template designed
to match the document element.