Fatal error: Cannot instantiate non-existent class: file_passwd in phpwiki/lib/WikiUserNew.php on line 2122

dear php-wiki team:

i'm having a problem getting going with 1.3.10 (current), which i downloaded today.  i've got everything set up and configured according to the docs, no problem, but when i load the main page, i encounter the following error:

<x-tad-bigger>Fatal error</x-tad-bigger><x-tad-bigger>: Cannot instantiate non-existent class: file_passwd in </x-tad-bigger><x-tad-bigger>phpwiki/lib/WikiUserNew.php</x-tad-bigger><x-tad-bigger> on line </x-tad-bigger><x-tad-bigger>2122

</x-tad-bigger>which refers to this code:

	// "__PHP_Incomplete_Class"
if (!empty($file) or empty($this->_file) or !isa($this->_file,"File_Passwd"))	    $this->_file = new File_Passwd($file, $lock, $lockfile);

i'm using php 4.3.6 on a gentoo linux box (kernel 2.4.21), against a mysql 3.2.1 database.  i should note that my previous phpwiki installation (1.2.something) worked fine against the same setup, and that this is a completely fresh installation (i.e. not an upgrade).

can anybody help me?

thanks!
-damian