After the demo content import you will the a page with the clear message: “All done!”
If you install the demo content and after your page stop to load and you can see only the WordPress admin area without content or you get an error message like “Error500″, the import process isnt finished. In this case just reload your browser to continue the import. Most shared hosting server are very slow and you can’t download all images in just 30 or 60 seconds (this is up to the PHP settings), so you have to repeat the import until all is downloaded. Please repeat this step until you can see the message:
Another solution is to import the demo content without images, this takes not so long and your server should be able to do this within some seconds.