Visual Studio - Debug gives error 0x800700b7

The issue: Upon trying to debug my site using Visual Studio 2012 and 2013, I receive the error "0x800700b7" telling me I have duplicate entries of an HTTP module in the web.config.

The attempted solutions:Microsoft's page on that particular error, http://support.microsoft.com/kb/942055, did not help my situation personally, but it might help you. It stated the error was caused by a duplicate entry in my ApplicationHosts.config. I checked this out, even though I have not touched the file, and it proved to be wrong.

I tried removing the changes I was working on prior to the error occurring, with no changes to the error issue. I did notice that a separate project of mine that was a mirror of the site before any changes was working just fine, so that told me it was a problem with just this project.

I tried replacing the web.config and the files I modified with the files from the unmodified site, just hoping that would resolve the issue and I could move on, that didn't work. I also tried just removing my copy and replacing it with a fresh copy of the working project. That didn't work, so I restored the copy that I was originally working with.

After trying each of these things repeatedly, I went to try adding a line to one of the config files as suggested here http://blogs.technet.com/b/tristank/archive/2013/03/07/iis-7-500-19-with-0x800700b7-cannot-add-duplicate-collection-entry.aspx. This did not fix the issue either and was removed, but I had opened the site instead of my solution folder and saved to a new Project/Solution. Once I removed the changes and saved, the issue was resolved. My assumption is that the solution file was corrupted at some point, but I have no way to confirm this. I hope this helps someone else and I apologize if this is done incorrectly, as this is my first time posting.

TL;DR: Try opening the website, not the project/solution, in Visual Studio and save it to a new solution.