Microsoft OMA Error 1503, Exchange 2003. Single Back End Server Set Up

Same error and issue as here:

https://www.experts-exchange.com/questions/22137589/Exchange-2003-OMA-Using-SSL-Application-Error-Log-Throws-1503-403-Forbidden-Error.html

However have followed these instructions to the letter, along with MS KB 817379 without any success.

Although the require SSL is unchecked, when browsing to test it still requests that is viewed over https.

When you do view over SSL  when authenticated we then get a "  A System error has occurred while processing your request. Please try again. If the problem persists, contact your administrator.".

If browsed via a mobile we just get page not found error.

OWA works a treat. The certificate created is home grown and not from a certification authority.

This is a last resort until we recreate the virtual directories according to KB 883380 I am reluctant to do this as OWA is functioning.

Any help/suggestions would be greatly appreciated.