Name: Time Warner Cable
Country: United States - Central Texas
Occurrence: Always

NOTE: I have already posted before, but I wanted to add something

Running a ping test before connecting to the launcher/login confirms I have a solid connection no matter what I am doing on the net
Immediately after starting FFXIV, the connection becomes completely unstable affecting my entire connectivity
As soon has I close out (or get kicked out) of FFXIV, my connection stabilizes again.

Running a simple ping test to another website before you open up FFXIV and leaving open during you attempt to get FFXIV, you should be able to see how its affecting connectivity.