When I test the availability of a document with:
 <xsl:template match="/">
        <xsl:choose>
            <xsl:when test="doc-available('http://www.w3schools.com/xml/note.xml' )">
                found
            </xsl:when>
            <xsl:otherwise>
                not found
            </xsl:otherwise>
        </xsl:choose>
from:<xsl:value-of select="document('http://www.w3schools.com/xml/note.xml')//from"/>
    </xsl:template>
On my Mac (OSX10.4.7) the result is "not found from:" on my windows laptop the result is "found from:jani"
It appears that absolute paths with http:// are not found on my mac but they are found with my windows laptop. When I check documents with relative paths or resolved paths (with file://) its OK, my mac finds the documents.
When I use the doc() function I get the error message:
Description: Failed to load document http://www.w3schools.com/xml/note.xml

I used the same network, same software (Oxygen) and same processor Saxon8B. (firewall stopped)
Anyone have a suggestion what I can do so the mac will find absolute path referenced

This is all to do with setting the right configuration properties for networking at the Java level, for example proxy server settings. It's hard to help with this remotely, and impossible when you're using a platform that I'm unfamiliar with. Google on the theme of Java networking system properties for Mac.

Michael Kay
http://www.saxonica.com/
Author, XSLT Programmer's Reference and XPath 2.0 Programmer's Reference