cpEIGetValue error

I have a large number of files with a button that launches a script.  Recently, I had to change all of them because window.open no longer worked.  My script now looks like this:

//<script type="text/javascript">

function launchwin() {

var SiteName="www.[DIRECTORY]";

var TipName="01_Creating_a_Letter/01_Creating_a_Letter";

document.location="http://"+SiteName+"/"+TipName+".htm";

}

//-->

//]]>

I'm not showing the directory on a public forum, but the link works if I patch it together manually, and the script works perfectly in other RoboHelp files.

In this project, however, it brings up an error message "Unable to set property 'cpEISetValue' of undefined or null reference."  Code 0

The error message also gives the URL for the link, which works correctly.

If I click "No" to the message about continuing to run scripts, it launches the link.  If I click yes, I'm stuck.

I've tried the script in several files in the project, and the same thing happens each time.

Has anyone seen this?  Any ideas?

It's a real problem for me - I'm going on a 3-week vacation this weekend, and the client wants the files quickly.

Thanks for any help!