HTTP 401 using WmXSLT

I’m running IS v6.1 on Windows XP. I encounter an HTTP 401 response code when executing both the WmXSLT samples and custom services that access the WmXSLT package. The 401 references attempts to access the .xsl file (stylesheetSystemId parameter of transformSerialXML). I’m accessing the .xsl using the URL http://localhost:5555/MyPackage/xdocs/myxslt.xsl. The .xsl is in the correct directory (otherwise I’d be seeing a FileNotFoundException).

Any ideas what’s going on? Is this an XP issue (probably), a v6.1 issues (unlikely), or what?

Dave Matlock