So, this interesting issue has been plaguing me for the past couple of hours. Visual Studio 2010 Ultimate no longer attaches the debugger and lets me debug my code.

If I use the built in development server, then everything works fine. If I switch to Use Local IIS Web Server (http://localhost/), then all it does it attach to w3wp.exe, but no DLLs or PDBs are loaded for anything. I can go to Debug > Windows > Modules, and literally nothing is loaded in this window. Conversely, when using the built in development server, the Modules window displays all the DLLs and shows that the symbols for my DLLs have been loaded. Something is obviously amiss. The VS installation is completely bone stock.

In IIS, my website is configured with ASP.NET 2.0 (because no 3.5 exists to select from the drop down), along with read / log visits / index this resource options checked on the "Home Directory" tab.

Some of my failed ideas:
1) If I attach to process on the iexplore.exe instance where the website is displayed, it loads Internet Explorer's DLLs, but not mine.
2) I've restarted the computer multiple times
3) I've invoked devenv.exe /resetuserdata once
4) I've confirmed that every project is indeed set to debug and not release.
5) Deleted all \bin contents and rebuilt the solution.
6) Deleted entire solution and repulled from Source Control.

Can someone tell me what is wrong with this thing? I'm going to have an aneurism from the headache this is causing me.