dispex SharePoint.OpenDocuments.3 works for PDF but not Office docs?

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XSLT

SharePoint2010

I have the folllowing in my XSL for a (SharePoint 2010) content query webpart:

<A onfocus="OnLink(this)" HREF="{$ItemUrl}"
onmousedown="return VerifyHref(this,event,'1','SharePoint.OpenDocuments','')"
onclick="return DispEx(this,event,'TRUE','FALSE','FALSE','SharePoint.OpenDocuments.3','0','SharePoint.OpenDocuments','','','','1','0','0','0x7fffffffffffffff')">
<xsl:value-of select="$DisplayTitle" /> (<xsl:value-of select="$ItemUrl" />)
<img src="/_layouts/images/blank.gif" class="ms-hidden" border="0" width="1" height="1" alt="Use SHIFT+ENTER to open the menu (new window)." />
</A>

What is interesting is that it opens the doc for a PDF doc but not an Office one?

Word/Excel/etc gives an error about the URL being malformed and it is because it is in this form:

http://blah.place.comhttp:/blah.place.com/site/subsite/doclib/docname.ext

And, no, the single / rather than // after the redundant http: is not a typo...

However, the onmousedown URL (and confirmed with me displaying the URL in brackets) looks correctly formed?

Basically, where is the call getting it's URL from as I have tried playing with the $ItemUrl to no avail (i.e. changing it to clip the server name, etc but the call still uses the same, erroneous one)?

Thanks in advance.