CFChart images broken when creating a PDF document with SSL

I have a report that I create with Coldfusion, that includes a number of CFChart objects.  I recently installed a new SSL certificate, and now all the charts show up as broken links.   It shows up fine if I try and display this as HTML. On the chance it was something weird about my (lengthly) report, I created the following sample code that I saved in a file called foo.cfm:

<cfset sDir = "C:/">

<cfset filename = "foo123.pdf">

<cfdocument format="pdf" filename="#filename#" overwrite="yes" marginleft=".7" margintop=".3" backgroundvisible="yes">

TEST 12345

<br>

<br>

<div style="height:500px;float:right; margin-left:10px; margin-top:10px; margin-right:10px; margin-bottom:10px;">

    <cfchart

        format="png"

        chartwidth="400"

        chartheight="360"

        showborder="no"

        databackgroundcolor="##ffffff" 

        fontbold="yes"

        sortxaxis="no"

        yoffset=".1"

        scaleto="100"

        showmarkers="no"

        show3d="no"

        fontsize="11"

          >

    <cfchartseries type="bar" datalabelstyle="none" seriescolor="##00CC99" paintstyle="shade">

    <cfchartdata item="B" value="40">

    <cfchartdata item="A" value="50">

    <cfchartdata item="E" value="80">

    <cfchartdata item="S" value="30">

    </cfchartseries>

    </cfchart>

</div>

</cfdocument>

<cfoutput>

<a href="#filename#" target="_blank">Foo</a>

</cfoutput>

If I go to the URL https://www.mywebsite.com/foo.cfm, the foo.pdf file shows a broken link.  If instead I go to http://www.mywebsite.com/foo.cfm the image of the chart shows up just fine. 

The weird thing is that I have an older server running CF9.0.0.  On this server it works just fine.  On another server with 9.0.1, it breaks.  Same with 9.0.2, and CF 10. 

I read something about needing to install the cert in a keystore, and I did this but it changed nothing.  The image is still broken in the pdf. 

Any help would be greatly appreciated.  We have been able to work around the issue by posting the image in a non-secure location, but this seems like a hack, not a proper solution.