I have a PDF attached to a post. I can open it with Firefox and Internet Explorer 6 but cannot open with Internet Explorer 7. All I get is a little x as though it's missing an image. I can open other PDFs with IE7 - just not the ones attached in a CBB post. Can someone help me figure this out please?

Thanks in advance.

EDITED TO ADD:

I just did an experiment. In 2.0.16 - in CBB the PDF opens just fine. In 2.2.4 CBB the PDFs do not open in IE7. Hopefully, someone can help??

EDITED AGAIN TO ADD:
Actually, I just tried it in another 2.2.4 site and the PDF opens fine. Something must be missing....? And yet it opens in other browsers. I just don't get it!