The maximum number of form, query string, or posted file items has already been read from the request. To change the maximum allowed request collection count from its current value of 2001, change the "aspnet:MaxHttpCollectionKeys" setting. See http://go.microsoft.com/fwlink/?LinkId=238386 for more information.

The maximum number of form, query string, or posted file items has already been read from the request. To change the maximum allowed request collection count from its current value of 2001, change the "aspnet:MaxHttpCollectionKeys" setting. Seehttp://go.microsoft.com/fwlink/?LinkId=238386 for more information.

 

ANSWER

somebody posted quite a few form fields to your page. The new default max introduced by the recent security update is 1000.

Try adding the following setting in your web.config's <appsettings> block. in this block you are maximizing the MaxHttpCollection values this will override the defaults set by .net Framework. you can change the value accordingly as per your form needs

<appSettings>
    <add key="aspnet:MaxHttpCollectionKeys" value="2001" />
 </appSettings>

for more information please read this post. For more insight into the security patch by microsoft you can read this Knowledge base article