strange base_url issue

[eluser]split[/eluser]
At the moment I got the feedback that HTTP_HOST is set and has the correct value normally. "Normally" means this was tested not in the codeigniter app. I use a workaround now. But if anyone has an idea why the code posted above could return just the path to the app I would like to hear about it. And, is this the only part where base_url is set or does another (core) script (mine definately not, just one controller with a few lines of code which I checked) perhaps overwrite or edit the value?

Thanks a lot!