reproduced in r2719.  customer reported bug.  he's trying to update a sub-rev-10
sb1.

broken from 5.3.0 and on, actually.  to get sub-10 fw upgraded you have to:
- use 5.3.0-5.4.1 to get up to fw 10.
- drop back to 5.2.1 to get upgraded to fw 29.
- go to 5.4.0+ to get up to fw 40.

This should fix it: 

Index: Slim/Player/Squeezebox.pm
===============================================================
====
--- Slim/Player/Squeezebox.pm   (revision 2720)
+++ Slim/Player/Squeezebox.pm   (working copy)
@@ -430,7 +430,7 @@
 
        if ((!ref $client) || ($client->revision <= 10)) {
                $::d_firmware && msg("using old update mechanism\n");
-               $err = $client->upgradeFirmware_SDK4($filename);
+               $err = upgradeFirmware_SDK4($client, $filename);
        } else {
                $::d_firmware && msg("using new update mechanism\n");
                $err = $client->upgradeFirmware_SDK5($filename);

Fixed for next nightly.  Please test with a pre-10 firmware player.