Error:
The URL-encoded form data is not valid.
Explanation:
The error is caused by the Windows update that was installed on your server recently.
Solution:
In order to resolve it just add the following text to the Easy Projects Web.Config file, to the <appSettings> section:
<add key="aspnet:MaxHttpCollectionKeys" value="10000" />
You can add the above string just above the following one:
</appSettings>
Refer to the Microsoft KB for details at http://support.microsoft.com/kb/2661403