I'm also been getting "ERROR: Password file not found" using superglue-firmware_0.1.36-RC-Athina_dir505a1_initial.bin
I found a typo in line 17 of the admin cgi file (/opt/lib/admin/admin2.cgi)
I changed the line:
readonly _PWDFILE="/etc/lighhtpd/htpasswd"
to
readonly _PWDFILE='/etc/lighttpd/htpasswd'
(change double quotes to single, correct spelling of lighttpd).
And it seems to have fixed the problem.