When attempting to resubmit an XML message (make sure you make the changes to the required stored procedures to set the correct content type for xml messages first, see http://midheach.wordpress.com/2012/03/23/esb-management-portal-customization/) to a receive location using the HTTP transport channel, you will get an error message saying that “A potentially dangerous Request.Form value was detected from the client”

This is because there are XML tags in the request message which would typically be considered unsafe.  Assuming your ESB Portal web site is only targeted at BizTalk administrator types you can always relax these restrictions by adding the below highlighted line into the web.config in your ESB Portal web directory.

Because these restrictions would effectively be relaxed on the entire website, this might not be ideal for everyone.  If someone finds a better way to get around this problem please let me know.