New HEAD common.inc causes "Home" link to not work anymore

After some investigation I noticed the problem comes from the function drupal_get_html_head function, so I looked after the differences between the two files.

The 1.511 version (the one which works and comes with Drupal 4.7 beta 4) looks like:

function drupal_get_html_head() {
  global $base_url;

  $output = "<m eta http-equiv=\"Content-Type\" content=\"text/html; charset=utf-8\" />\n";
  $output .= "<base href=\"$base_url/\" />\n";
  $output .= theme('stylesheet_import', 'misc/drupal.css');

  return $output . drupal_set_html_head();
}

The 1.515 version (latest HEAD which does not work) looks like:

function drupal_get_html_head() {
  $output = "<m eta http-equiv=\"Content-Type\" content=\"text/html; charset=utf-8\" />\n";
  $output .= theme('stylesheet_import', base_path() .'misc/drupal.css');
  return $output . drupal_set_html_head();
}

So I changed the function like this:

function drupal_get_html_head() {
  global $base_url;
  $output = "<m eta http-equiv=\"Content-Type\" content=\"text/html; charset=utf-8\" />\n";
  $output .= "<base href=\"$base_url/\" />\n";
  $output .= theme('stylesheet_import', base_path() .'misc/drupal.css');
  return $output . drupal_set_html_head();
}

In fact I did a mix between the two versions. And now I have the correct home path, and the add view still works.
But I'm not a specialist, so I'm afraid what I did could have bad consequences on other modules, so if a specialist could look after this function and tell me how to fix it.

Thanks

What module are you talking about?
The problem occurs when I installed 1.515 version of common.inc over my 4.7 beta 4 version of drupal...
So, what do I have to upgrade so the home page will work even with the 1.515 version of common.inc?

So, I should upgrade my drupal site to CVS HEAD version?
How do I do this, without copying all the files one by one?

Thanks

I'm trying to have the lastest version for now... my site is not in production, I'm migrating from SPIP to drupal, so for now I'm testing drupal, I'm creating my articles, and once my site will be ready I'll replace SPIP website by this one...

I'm currently upgrading it to latest CVS... because I need the insert view module, and this module does not exist in 4.6.5... and the latest CVS is far cooler than the 4.6.5 ;)