Xbox360 users lag like crazy during Reives

Platform: Xbox 360
ISP: Frontier Communications
Type of Internet Connection: DSL
Internet Connection Speed: 120MBS (according to the router)
Date & Time: During Colonization Reives with 20+ players
Frequency: Depends on the amount of players
Character Name: Majormeowmix
World: Shiva
Main Job: Dancer
Support Job: Ninja
Area and Coordinates: Ceizak Battlegrounds (G-7) (G-8) (G-9) (I-8)
Party or Solo: either
Monster Name: Floodplain Spider, Lightfoot Lapinion, Lavender Twitherym, Bounding Chapuli
Steps:
1. Start Reive
2. players enter
3. Major game/UI lag


(Once in awhile it will also freeze)

I am re-posting this do to not formatting it right on the original post.

There are two areas which could cause the symptoms that you're describing.
The first would be the system hardware or software. Of course make sure that there aren't any overheating or dust problems to start. Sadly, since the XBOX 360 version of the game is mainly plug and play we can only ask you to clear the system cache, make sure there is enough hard drive space, and if all else fails, re-install the game.

The second, and more likely, source could be the connection. Please take a look at our suggestions to see if there are any changes you can make to your network environment:

1. Check to make sure you have properly configured any of the following: Routers, Proxy Servers, NAT Servers, Internet Connection Sharing services.
2. If you are using any kind of software/hardware Internet Sharing service/device the following ports need INCOMING access to your PC: TCP 1024 - 65535, UDP 53, and 50000 - 65535. Also, check to make sure that the ports mentioned are not blocked by your ISP for INCOMING access. Proper configuration of any of the above items mentioned should be done by following the instructions in the software/hardware manual or calling the manufacturer's technical support.
3. If you are using a router, and have configured that router for port forwarding, temporarily bypass that router and connect directly to the modem.

Please take note of the following:
• Proxy servers, and satellite connections are not supported and do not work correctly with FINAL FANTASY XI.
• Your router may require that you use a PC to configure your network settings. For more information about how to configure your network settings, please refer to the instruction manual that came with your router or contact the manufacturer directly.