In case someone stumbled upon this problem:

1. You download and install the new release of phpBB (3.0.9) and immediately integrate SEO Ultimate URL package
2. The setup went well except you found out that the page is looked ugly because the CSS wasn’t loaded – cause by the URL got backslash in it:

http://localhost//style.php …

To fix, you need to edit the data in the config table:
1. Access the phpBB3 config table (phpbb_config)
2. Lookup for config_name = ‘script_path’
3. You’ll see the value is ‘/’. Change this to ‘/’
4. Save the data

Clear the cache, and reload the page. You should see the pretty page back again!

Additional: I’m using localhost with custom port number (82) as testing platform. So in case you’re not getting the image out on the page (caused by the URL generated become http://localhost/style… instead of http://localhost:82/style…, so you need to edit the force server URL settings

1. Go to admin control panel, General > Server Settings
2. Set ‘Force Server URL’ to ‘Yes’