Ugh, since I installed a new machine I ran into this error message above earlier. That's a pretty omnious sounding error message which seems to hint at a mis-configuration during installation. The error occurs as soon as you try to debug a Web application against IIS 7...

As it turns out the problem is much simpler:

IIS 7 installs without Windows Authentication enabled. Without proper authentication Visual Studio can't effectively validate against IIS in order to get the appropriate rights to start the rather intrusive debugging process against IIS and so it fails.

The error message is a bit misleading and in fact my first thought was that during setup some assembly didn't get properly signed. I was already reaching for sn to start signing assemblies <g> or bypassing signing checks. Yuch.

Oddly the error message for this particular scenario has been changing over time. I have run into this before - with Win2003 server I believe although at the time the error message was even more out in left field.

To be fair though the help topic that pops in Orcas does point in the right direction if you read carefully through the Setting up for Debugging topic. Seems this particular issue will be common enough though that it should be at the top of the list.

Thankfully an easy one to fix.