Game doesn't run a correct fps

Game doesn't run a correct fps

so I am making a simple 2d game in Java. I am only using 1 thread and set
the game to run off 120 fps, since this game isn't resource heavy almost
any computer should be able to run this, infact my friends computer thats
like 8 years old can run it at 120fps, but I can't, well not always, I
know my computer is fast enough, it a home built computer with really good
specs. At first it was able to run it easily at 120 fps, but lately when I
try to run the game it stops at 63-64 fps, I have made no changes to my
games code since it was running at 120 fps. I am not using any libraries
I'm just using Graphics g2d and sprites.
I don't know really what code I should include, this is my main thread:
time = new Timer(8, this);
time.start();
I also included my jar file which can be ran(for testing of fps) or
decompiled. (http://www.4shared.com/file/pdXXyxr8/Game.html) I know this
is a kinda bad post but I really don't know what to include it a really
odd problem that seems to be more related to runtime and random
probability then code.