I am testing enabling Advanced URL management on our QA server (which is an exact copy of our production environment), and when I switch from "humanfriendly" to "advanced" in the web.config, I get the following error for ALL pages except the home page:

A potentially dangerous Request.Path value was detected from the client (:).

Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.
Exception Details: System.Web.HttpException: A potentially dangerous Request.Path value was detected from the client (:).
Source Error:
An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.
Stack Trace:
[HttpException (0x80004005): A potentially dangerous Request.Path value was detected from the client (:).]
System.Web.HttpRequest.ValidateInputIfRequiredByConfig() +11489803
System.Web.PipelineStepManager.ValidateHelper(HttpContext context) +184

Version Information: Microsoft .NET Framework Version:4.0.30319; ASP.NET Version:4.0.30319.261

The URLS look like this when I go to any of the other pages other than the homepage: https://q-corpsite.swbc.local/pagenotfound/tabid/1590/404;https://q-corpsite.swbc.local:443/our-products-services/language/en-us/default.aspx yet this is the URL I click on via the nav: http://q-corpsite.swbc.local/Our-Products-Services

Why is it adding in en-US... localized content is NOT enable on this site.

Stumped at what is causing this. 

Thanks in advance.

I did verify it is set to "2.0".....

This is very frustrating, as I can't risk moving the production site to "advanced" mode without verifying to works in the QA environment. It is still generating the error above... except the homepage, which loads fine.

So as I mentioned an example link in the nav like(or any link in the controlbar if logged in) goes that error:

Example:
http://q-corpsite.swbc.local/our-prod... goes to the error page and
generates this in the address bar:
http://q-corpsite.swbc.local/pagenotf...;http://q-corpsite.swbc.local:80/our-p...

Is there a reason it is trying including "/language/en-us/default.aspx" in the URL when it would be looking for the "https://www.swbc.com/OurProductsServi... in the old humanfriendly format?

This might help somebody. I just had this same error message and for me it occurred only when clicking a linked pdf with a complicated file name. After I shortened the name and removed the &, -, ( and) from the file name, the error no longer appeared.