If you are using a skin to make your UI look pretty, you may have noticed that all your skill bars go nuts when you resize your the game while in window mode.
You can lock your window size so this no longer happens.
In your My Documents folder/ The Lord of the Rings Online folder, under all your screenshots is a UserPreferences.ini file.
Right click this file and open it with Notepad.EXE or Word.EXE
Search for this option. AllowWindowResizing=True
Change it to this. AllowWindowResizing=False
This should lock your window so it can not be resized.
This file will be updated and erase your setting. So if your bars go nuts again, just re-edit this file and your good to go!