It took me a while to work this out, but I finally got it...

If you are using Windows XP ( I don't know if this will work on Vista...) and are having issues with Lag, especially in the Chat window, the fix is really fairly easy.

Evony, it turns out, hides a lot of Temporary and Log Files inside your Documents and Settings.

Goto your Prime Harddrive ( C: for most people) then to Documents and Settings, your Log-in name. If you have files set to Unhide, you will see a folder named Local Settings. There is a second Temporary Internet Files folder in there. Enter this folder, and delete all of the files. Clearing the Cache, a method that has been suggested before, does not touch these files.

As soon as I did this, all of the "Lag" that has been happening vanished.

I hope this helps people who have been frustrated by the Lag...