BYOND Build Number: 493.1117
Operating System: WinXP SP3
Video/Graphics Card: nVidia 9800 GT
Internet Connection Type: ADSL2+ 5Mbit
Firewalls/Routers: ESET Smart Security, router: Billion BiPac 7300 G

Problem Description:
After a certain amount of inactivity whilst being connected to non-locally hosted games, the data flow between the client and the server seems to freeze. There is no immediate connection failed message, and commands seem to go through for a while but nothing seems to happen. This even occurs when connected through telnet, but on telnet the connection doesn't seem to break off unless I close it manually.

Steps to Reproduce Problem:
1. Join a BYOND game
2. Stay AFK for a while. Sometimes it takes 15 minutes, sometimes 40. It's fairly random but usually above 10 minutes.

P.S. It has recently often occured to me when I'm idle in (This is not a plug for my chat thing! :P) Other users seem to be fine.
If you are getting random drop times, It looks like there is a good chance your router is dropping the connection.

Are you using the wireless, or Ethernet cable?

If your using the wireless, do you have the latest version of the firmware installed?

One of the reviews I found on the internet about that router explained they were suffering from unexplained drop outs before updating to 1.35 (may or may not be the latest firmware version)
In response to Higoten
I'm using Ethernet.

The router's current firmware version is 1.36. I found a 1.38 for the 7300 GA but that doesn't seem to be compatible with this model.

Also, after some testing, this doesn't seem to occur to other computers on the LAN. The ones I tested were also using ESET Smart Security for the firewall.
In response to Metamorphman
Alright, that is good to know that its most-likely not your router.

Unfortunately I'm not quite sure what else would cause a random disconnect while idling.

Do you have any parental controls enabled? It is possible that any over protective control might kick your connection if any inappropriate words are received.

Do you have a screen saver enabled? I've seen instances when I would leave DS running while a screen saver would appear and 7-8 hours later DS would disconnect itself.