2 Comps 1 connection

Okay, so my friend lost internet access, because his service provider shut down, And I have a second computer. If I hook them both up to one router will both be able to run GW, and be allowed to enter the server? It was my understanding that many online games will block an IP, if the same one is already logged in.

Nope.
Guild wars is based on account, not ip-based, so provided you both have an account then you can both log in and play.

I've accidentally logged in from another computer without logging out from another, and all that happens is that the previously logged in avatar gets disconnected.

Yes, it will work, so long as each of you have your own copies of GW with unique CD keys. I'm running a D-link DGL-4300 rounter/FW and sharing my one cable modem between my two PC's. Me and my wife are able to both party in GW just fine.

Huh? What?

Using someone else's computer to play GW doesn't involve having GW disks or even CD keys. Once you've bought GW and established your account, you can visit anyone's computer, download/install the client from guildwars.com and play using your account/password.

It's that easy.

If GW is already installed on a system, just use YOUR username/password and play away.

Also, to answer the OP. You can install GW on every computer on a LAN behind the router and have that many different accounts all playing their own GW accounts at the same time. (I've copied one installation of GW to my 2GB USB stick and have moved it to several different systems on a local LAN...it saves a lot of bandwidth)

They talking about playing at the same time, not taking turns...

Okay thank you, just wanted to clarify, before I started hooking everything up.