Although it appears that many questions on this board get no answers, I am an eternal optimist...
I am using the following to open a file (x.htm).
IFileStore fileStore = ...
IWorkbench wb = PlatformUI.getWorkbench();
IWorkbenchWindow window = wb.getActiveWorkbenchWindow();
IWorkbenchPage page = window.getActivePage();
When I run the application from the development environment, this file is opened inside the Eclipse window as expected.
When I run the exported application, the file is opened in a separate browser window.
I have used Organise Manifests... on all the MANIFEST.MF files in my project to ensure they are up-to-date.
Can anyone suggest why I am getting this difference in behaviour?