Ok! For everyone who doesn't understand all this, I made some graphics to help:
Here is what Artem is saying:
The SE FFXI Servers are self-explanatory, multiple computers comprise vanadiel. You are at home on your computer. Me is at home at my computer.
The Internet is made up of small ISPs that all hook up to a backbone. Think of it as America's roads with many small roads that lead to the bigger Interstates. UPS travels across those roads. So does the information between computers.
See the big black circle where the connection is broken? Now Follow the paths.
Me - I can get to Windy easy, my computer for some reason makes me go the green route to FFXI Server and Back. However, if I follow the purple, It sends the information but never gets back to me, thus I can't seem to get into Sandy.
You - For some reason your packets get routed, based on your IP/where you are, for both Windy AND Sandy through that broken area. Well, sucks to be you, because you can't get those packet informations back.
So you're sending information to the server, but somewhere on the way back, you can't get any of that information, so ultimately the game drops you.
In this scenario, a lot of people have been toying with MAC Addresses and changing IPs. Changing IPs can help because it may change the way you route your way to the server and back, and fix those problems. BUT, now you run the risk of possibly re-routing how you got to bastok computer.
Think of it as UPS trying to find the quickest best route to deliver information and packages to and from your home to your destination.
Here's Scenario 2:
Information is sent along those lines from the first graphic in little packets. It's like shipping letter after letter from UPS across the nation, and you collect all the letters and it forms a book telling you what to do.
Somewhere along the line back, the packets destination, or the header, or something related to it is all messed up so it never comes back to you. For example you send all the letters across the nation, but they address it to you at the wrong address. Well, now you never get any of those letters back. Or maybe you do get the letters back, but the content is all junk, and you have the wrong letters you need.
That's also a possibility. In fact we don't know the code, or how it's done, so we don't really know anything at this point.
In fact, we basically don't know. It's all speculation what the problem is. Hell it could be a combination of both issues. Whatever problem is we need to remain calm and wait it out. BUT, SE could handle it better by addressing customers and not tossing us to the side. Also, for the record they were mum about it the whole weekend. I left Saturday morning and they didn't admit to it, I came back late sunday night and they still didn't. They only started fessing up to problems monday morning.