Hmmm at a glance everything looks in order. This doesn't have anything to do with whether IE thinks the external pages are off domain, as in those cases it simply won't load the specified page, whether in the content DIV or as its own page. It looks like something else on your page is cancelling out the "onclick" event handler that's dynamically assigned to each of the tabs when the page loads. To confirm if the problem could be one of your other scripts on the page, try temporarily removing them:
Code:
<script type="text/javascript" src="http://www.dgglobal.ca/IMPACT/JsScripts/stdJavascripts.js"></script>
<script type="text/javascript" src="http://www.dgglobal.ca/IMPACT/JsScripts/x_core.js"></script>
<script type="text/javascript" src="http://www.dgglobal.ca/IMPACT/JsScripts/x_event.js"></script>
<script type="text/javascript" src="http://www.dgglobal.ca/IMPACT/JsScripts/x_window.js"></script>
<script type="text/javascript" src="http://www.dgglobal.ca/IMPACT/JsScripts/x_dom.js"></script>
<script type="text/javascript" src="http://www.dgglobal.ca/IMPACT/JsScripts/cal.js"></script>
<script type="text/javascript" src="http://www.dgglobal.ca/IMPACT/JsScripts/en/cal_conf.js"></script>
BTW, please note that your page is currently in violation of our usage terms, since the credit notice doesn't appear inline on the page. Please reinstate the credit notice:
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