Sudden Bad Request - Invalid Verb on during debugging Visual Studio

Question

During development I suddenly started to receive following error message

Bad Request - Invalid Verb

HTTP Error 400. The request verb is invalid.

The website under development was run on ISSExpress via Visual Studio. It stopped working out of the blue, without any changes in the configuration.

I'm using: ASP MVC, C#

What can be the cause?

Answer 1

It turned out that the problem was caused by... an invalid cookie.

The solution was to remove all cookies.

(I accidentally checked the page on other browser and it worked there.)