The error messages says it can't find the hook 
_username_hook_tobackend. Either you activated the wrong hook in 
Horde's configuration, or you gave your hook method the wrong name.

I did a cvs update -dPCAR to update everything recursively, replacing 
everything with clean copies from HEAD, building new directories, and 
pruning empty directories.



I then ran the install-packages.php script from framework.  Everything 
installed okay, with the following informational messages:



horde/Horde_Auth can optionally use PHP extension "pam_auth"

horde/Horde_Auth can optionally use PHP extension "sasl"

horde/Horde_Browser can optionally use package "horde/PEAR"

horde/Horde_MIME can optionally use package "horde/Horde_Identity"

pear/Net_SMS can optionally use package "pear/Net_SMPP_Client"

horde/Horde_Secret can optionally use PHP extension "mcrypt"

warning: horde/Horde_Share requires package "horde/Horde_Identity"

warning: horde/SyncML requires package "pear/XML_WBXML"

horde/Text_Diff can optionally use PHP extension "xdiff"



I don't know where "horde/Horde_Identity" is supposed to come from.   
Also, I don't know why horde/SyncML complains about XML_WBXML because 
XML_WBXML is installed okay.  Maybe SyncML should be depending on 
"horde/XML_WBXML" instead of "pear/XML_WBXML"?  Just a guess.



I added a var_dump right before the line in question in Auth.php, and 
I've attached the output from it (with my password stripped out).

I can't see any place in the code that could lead to a PEAR_Error 
being passed to that line of code. Make sure that all your code is 
uptodate, the newest framework packages installed and any bytecode 
cache disabled.

Here's the only hook I'm using:



if (!function_exists('_username_hook_frombackend')) {

        function _username_hook_frombackend($userID) {

                if (strpos($userID, '@') === FALSE) {

                        $userID .= '@oxmoor.com';

                }

                return String::lower($userID);

        }

}

I don't know.  I use IMAP for authentication, if that makes any difference.

So the question is, why is your system passing an error to 
Auth::authenticate instead of a username? Are you using hooks, perhaps?

All authenticated pages in Horde have this notice at the top:



Notice: Object of class PEAR_Error to string conversion in 
C:\PHP5\PEAR\Horde\Auth.php on line 139



This is especially bad because it is also present in the binary 
streams returned by file attachment downloads, which of course 
corrupts the file.