"Forcing Client Reconnect <6>" and people getting disconnected

[Slygathor]

Hi all, I've been running and SRCDS TF2 server for well over a year now, and I've had no issues up until recently. Every time I go to check on my server I keep seeing "Forcing Client Reconnect <6>", and some of my friends are reporting they get disconnected shortly after downloading the maps and/or plugins. But other people have no problems joining my server. Here's some of my server info:
Server OS: Windows Home Server x86
Processor: Pentium 4 2.80GHz and it should be threaded.
Ram: 512MB
Game(s): Team Fortress 2
Start Up Command: C:\HLServer\orangebox\srcds.exe -console -NoQueuedPacketThread -game tf -hostport 27015 +maxplayers 24 +map name of map (It changes weekly; I run Harbl_Hotel, cyberpunk, MARIO_KART, ctf_2fort, and achievement_idle)
Admin Mods: Metamod and Sourcemod
Network Info:
External IP: 74.101.144.2
Internal Server IP: 192.168.1.126
Port Forwarding: I Have my server IP added as a DMZ, to avoid forwarding all the necessary ports.
Network Configuration:
Router/Modem: Actiontec FiOS MOCA router.
[Server]->[Router/modem]->[Internet]

Any and all help is greatly appreciated.
Thanks,
Slygathor