I'm having a similar problem. In my case, when opening help the first time (using a call to RoboHelp_CSH.js), the help window works properly. If I do not close the help window and click a help link (same call to RoboHelp_CSH.js), the help window blanks out entirely. I'm not sure if roblinc61 has a different copy of the whcsh_home.htm file than I do, but line 295 for me is three lines lower (goNewWnd.document.location.href=gsURL;).
The only answers I've been able to find about this error message relate to the same origin policy which should not apply to me as I am building an intranet application in which the help is held in a directory of the main site and is accessed through relative paths (in .NET I'm setting the starting point as ~/Help/index.htm).
Interesting – I’m getting the blank page too & 2 additional fully-skinned browser windows spawned off also. They both have the content of the second topic launched; the first window’s CSH content is gone. Guess most of my users close the first window before launching the help again in another spot.