I can't remember what the chat frame is actually called in game, so I can't provide code to move it, nor did a quick perusal of the RoM Wiki reveal anything.
However, there is something else you could do. Exit the game and open the file SaveVariables.lua in any text editor (it's in Documents and Settings under a hidden folder called Runes of Magic). Search through this file and find where it saves the position of the chat window and modify the values directly (something like a position of 100,100 should put it somewhere usable). Save your changes then when you start the game, it should be in the new position. You can then move it to where you want.