BFLy on "[Plugin: W3 Total Cache] HTTP/1.0 401 Authorization Required"

if used xcache, edit your xcache.ini and change xcache.admin.enable_auth = On to xcache.admin.enable_auth = Off:

;xcache.admin.user = "admin"
;xcache.admin.pass	= "hash-password-here"
xcache.admin.enable_auth = Off

and restart apache.