I tryed to say that your installation needs to be greater than 5.4.x to run asp.net 4.

If yor webconfig did not change maybe the bug occured.
Look in webconfig or you could test if you get the captcha image to work with the feedback module just as an example.

Have you verified in Host Settings or the Host Dashboard that your site is actually running under ASP.Net 4.0?

There should actually be three changes made to web.config when switching the site's AppPool to ASP.Net 4.0 as indicated in the Install\Config\Net40.config   XmlMerge source file. These include the one related to the setting of the requestValidatioMode which you found plus two in the configuration/runtime/assemblyBinding section relating to bindingRedirects for System.Web.Extensions and System.Web.Extensions.Design.

Another change which should be made but is not and to which Jan is referring is found in the system.webServer/handlers section of web.config. Any appearance of

preCondition="integratedMode,runtimeVersionv2.0"

should be changed to

preCondition="integratedMode,runtimeVersion4.0"

If that is not done, any attempt to reference for examle the LinkClick or Captcha handlers will result in either a 404 resource not found error or a missing Captcha image.

Regarding the addition of requestValidationMode="2.0" in the httpRuntime section, the need for that will not be noticed except when certain resources other than .aspx pages are accessed - in particular web services and some HTTP handlers.

Here are a couple of resources for ASP.Net 4.0 migration issues:

http://msdn.microsoft.com/en-us/libra...
http://msdn.microsoft.com/en-us/libra...
http://www.asp.net/learn/whitepapers/...

In some of the older modules which I developed I have run into several issues with invalid html markup (particularly mismatched quotes), code access security violations (im implementation of ISerializable interface), and the change in request validation.

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Bill, WESNet Designs
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