diff -up firefox-31.3.0/mozilla-esr31/extensions/auth/nsAuthSambaNTLM.cpp.old firefox-31.3.0/mozilla-esr31/extensions/auth/nsAuthSambaNTLM.cpp

--- firefox-31.3.0/mozilla-esr31/extensions/auth/nsAuthSambaNTLM.cpp.old	2014-11-25 12:23:22.000000000 +0100

+++ firefox-31.3.0/mozilla-esr31/extensions/auth/nsAuthSambaNTLM.cpp	2014-12-23 15:26:36.606674625 +0100

@@ -174,7 +174,7 @@ nsAuthSambaNTLM::SpawnNTLMAuthHelper()

         return NS_ERROR_FAILURE;

     const char* const args[] = {

-        "ntlm_auth",

+        "/usr/bin/ntlm_auth",

         "--helper-protocol", "ntlmssp-client-1",

         "--use-cached-creds",

         "--username", username,