WebHelp Blank Page in IE11

I have upgraded a WebHelp project supporting a browser application from RoboHelp 9 to Robohelp 11.02.240.

The WebHelp context sensitive help displays and refreshes correctly when the browser application is opened in Firefox and Chrome.

The following error occurs when the browser application is opened in IE11:
1/ The first time a help button is selected on the application the help window displays correctly.
2/ But leave the help window open and select a help button on the application and the help window does not refresh correctly. A Blank Page is displayed. 
 
The browser application uses the RoboHelp_CSH.js file and the RH_ShowHelp function with the HH_HELP_CONTEXT command.

I have provided my software developers with the lastest RoboHelp_CSH.js file shipped with RoboHelp 11.02.240.

This is an old application and the help did display correctly in IE when it was developed. I dont know which IE release introduced the problem.

Is there a fix? Thanks.