I am trying a simple example of loading http://bing.com
in the html placeholder (which is inside a tile view item). I am using Q2 2010 release.
At first I thought if was a generic problem with Bing in iframe but I tried it using the iframe demo at http://www.w3schools.com/tags/tryit.asp?filename=tryhtml_iframe
and it worked without error messages.
I get the IE dialog about debugging and if I ignore the error, everything seems to work correctly from that point on.