[Serusers] SER + Asterisk; BYE gets 404

I am running ser 0.9.6 on CentOS 4.2 with asterisk on the same box listening on 5065. When I register a phone with ser, I can call XXXX(a)pbx.nexusmgmt.com and these calls are forwarded to the asterisk on a forward(<external IP>,5065). I've attached my full routing block below. After hanging up from either phone, the BYE packet never gets delivered. It shows up in ethereal as being addressed to the external IP address of the box and it gets a 404 in reply. When I register a phone directly with the Asterisk, I can hang up from either end as normal, so the issue must be with ser. Any hints on how I can route the BYE packets correctly? Thanks, Bart... route { # ----------------------------------------------------------------- # Sanity Check Section # ----------------------------------------------------------------- if (!mf_process_maxfwd_header("10")) { sl_send_reply("483", "Too Many Hops"); break; }; if (msg:len > max_len) { sl_send_reply("513", "Message Overflow"); break; }; # ----------------------------------------------------------------- # Record Route Section # ----------------------------------------------------------------- if (method!="REGISTER") { record_route(); }; # ----------------------------------------------------------------- # Loose Route Section # ----------------------------------------------------------------- if (loose_route()) { t_relay(); break; }; # ----------------------------------------------------------------- # Call Type Processing Section # ----------------------------------------------------------------- if (uri=~"sip:[0-9]{4}@pbx\.nexusmgmt\.com") { forward(65.126.236.148,5065); break; }; if (uri!=myself) { route(1); break; }; if (method=="CANCEL") { route(1); break; } else if (method=="INVITE") { route(3); break; } else if (method=="REGISTER") { route(2); break; }; lookup("aliases"); if (uri!=myself) { route(1); break; }; if (!lookup("location")) { sl_send_reply("404", "User Not Found"); break; }; route(1); } route[1] { # ----------------------------------------------------------------- # Default Message Handler # ----------------------------------------------------------------- t_on_reply("1"); if (!t_relay()) { sl_reply_error(); }; } route[2] { # ----------------------------------------------------------------- # REGISTER Message Handler # ---------------------------------------------------------------- sl_send_reply("100", "Trying"); if (!www_authorize("","subscriber")) { www_challenge("","0"); break; }; if (!check_to()) { sl_send_reply("401", "Unauthorized"); break; }; consume_credentials(); if (!save("location")) { sl_reply_error(); }; } route[3] { # ----------------------------------------------------------------- # INVITE Message Handler # ----------------------------------------------------------------- if (!proxy_authorize("","subscriber")) { proxy_challenge("","0"); log(1,"authenticate please\n"); break; } else if (!check_from()) { sl_send_reply("403", "Use From=ID"); break; }; lookup("aliases"); if (uri!=myself) { route(1); break; }; if (!lookup("location")) { sl_send_reply("404", "User Not Found"); break; }; route(1); }