[SOLVED] Web Forms For Marketers Form Designer throws 'Handle Not Found' Error

Web Forms For Marketers Form Designer throws 'Handle Not Found' Error

In Sitecore 7.2, opening FormDesigner gives the following error:

Exception: System.InvalidOperationException
Message: Handle not found.
Source: Sitecore.Kernel
   at Sitecore.Web.UrlHandle.Get(UrlString urlString, String handleName, Boolean removeSessionValue)
   at Sitecore.Form.Core.Utility.Utils.GetDataSource(String url) in C:\Users\Raymond.Weng\AppData\Local\JetBrains\Shared\v01\DecompilerCache\decompiler\DA67A299-0E6A-4A9B-A8E1-031DAB1327EB\e6\7823a5d7\Utils.cs:line 219
   at Sitecore.Forms.Shell.UI.FormDesigner.GetCurrentItem() in C:\Users\Raymond.Weng\AppData\Local\JetBrains\Shared\v01\DecompilerCache\decompiler\DA67A299-0E6A-4A9B-A8E1-031DAB1327EB\a8\50ab1903\FormDesigner.cs:line 723
   at Sitecore.Forms.Shell.UI.FormDesigner.LoadControls() in C:\Users\Raymond.Weng\AppData\Local\JetBrains\Shared\v01\DecompilerCache\decompiler\DA67A299-0E6A-4A9B-A8E1-031DAB1327EB\a8\50ab1903\FormDesigner.cs:line 163
   at Sitecore.Forms.Shell.UI.FormDesigner.OnLoad(EventArgs e) in C:\Users\Raymond.Weng\AppData\Local\JetBrains\Shared\v01\DecompilerCache\decompiler\DA67A299-0E6A-4A9B-A8E1-031DAB1327EB\a8\50ab1903\FormDesigner.cs:line 128

Request information: 
Request URL: http://myurl/sitecore/shell/Applications/Modules/Web Forms for Marketers/Form Designer?xmlcontrol=Forms.FormDesigner 
Request path: /sitecore/shell/Applications/Modules/Web Forms for Marketers/Form Designer 
User host address: xxx.xxx.xxx.xxx 
User: sitecore\admin 
Is authenticated: True 
Authentication Type:  
Thread account name: NT AUTHORITY\NETWORK SERVICE

I think something is wrong with the installation, but comparing the instance with the WFFM install files, I cant see whats missing. Not even sure what Handle Not Found means?

Solution

This ultimately came down to the URL. Sitecore was set to inject the language into the URL automatically (This is a setting in the linkManager section of the web config). WFFM really didnt like this. When I changed that setting, everything was fine.

UPDATE

An example patch would be:

<configuration xmlns:patch="http://www.sitecore.net/xmlconfig/">
<sitecore>
    <linkManager>
        <providers>
            <add name="sitecore">
                <patch:attribute name="languageEmbedding">never</patch:attribute>                   
            </add>
        </providers>
    </linkManager>
</sitecore>