Symptoms

After upgrading to 4.6.9, Smartforms on runtime keeps on loading when opened in IE11 and IE10. This behavior does not persist on other browsers such as Chrome.
 

Diagnoses

This is caused by a missing key (AnonymousResources.ashx) in the runtime web.config file
 

Resolution

Edit the runtime web.config file as described below.

Locate the following section:

<add key="Forms.Compression.ExcludedPatterns" value="Image.ashx;UserImage.ashx;File.ashx;ResourceJson.ashx;UserResources.ashx;SharedResources.ashx;CombinedResource.ashx" />

And change it to:

<add key="Forms.Compression.ExcludedPatterns" value="Image.ashx;UserImage.ashx;File.ashx;ResourceJson.ashx;UserResources.ashx;SharedResources.ashx;CombinedResource.ashx;AnonymousResources.ashx" />

Perform iisreset to apply the changes.