Does the update procedure of IBM Rational Robot update the RobotLogStyleSheet.xsl in the project's log folder?
The OpenComparator link in the HTML log is absent or you get error messages when you click the link. The update procedure does update the RobotLogStyleSheet.xsl in the Rational Test folder.
In the current situation, you need to copy the RobotLogStyleSheet.xsl manually from the folder Rational Test..
This function has been identified as a request for enhancement (RFE) under RATLC02512287.