Fatal error: Call to undefined function: filter_xss_bad_protocol

From http://drupal.org/node/57141#comment-108327
I believe this is the new look of the old Fatal error: Call to undefined function: user_access() in [path]/common.inc.

Possible causes

1. The upload of drupal didn't finish correctly; try reuploading the files.
2. modules directory is not readable by apache
3. Your php installation is broken (it doesn't use foreach correctly).

(1. is the most likely cause).

To test 3, make a file called test.php with the contents:

$a = array (1, 2, 3, 17); 

foreach ($a as $v) {
  print "Value of \$a: $v.\n";
}

Upload this to your server and direct your browser to http://example.com/test.php

If the output doesn't look somewhat like:

Value of $a: 1.
Value of $a: 2.
Value of $a: 3.
Value of $a: 17.

but repeats the word array, like this:

Value of $a: Array. Value of $a: Array. Value of $a: Array. Value of $a: Array.

Then the problem is 3, often caused by an incompatible optimizer.

--
Tips for posting to the forums.
When your problem is solved, please post a follow-up to the thread you started.