The server was unable to save the form at this time. Please try again.

This is one of the issue, which was scratching our production support team's head for a long time, today we found out the resolution.

Issue

When we try to add a new sharepoint list item in sharepoint 2013 environment, we get the error popup is "The server was unable to save the form at this time. Please try again."

Resoultion

1. Edit your web.config of your sharepoint site
   
   The path location is
   
   Drive\Inetpub\Wwwroot\WSS\VirtualDirectories\<port number of your web-application>\web.config
   
   
2. Add the entry
   
   <serviceHostingEnvironment aspNetCompatibilityEnabled="true"/>
   
   
3. Save the changes
   
   The issue is resolved. we are able to add sharepoint list items with out any issues.

Happy SharePointing :-)