The XSL include Files
Note that the beginning of the CWEditPropDlg.xsl file contains the line (shown in bold below):
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
version="1.0" ><xsl:include href="CWCommon.xsl"/>
The include line references the CWCommon.xsl file in a relative path; that is, the application expects to find the file in the current directory since none is specified. If the CWCommon.xsl file is not found, the following error is displayed in lieu of the Modify Properties pop-up window shown above.
To account for this, if you are customizing CWEditPropDlg.xsl, the CWCommon.xsl file must be in the same directory (web > cw > custom) as the CWEditPropDlg.xsl file that references it.