(Java) Timer objects 'running slow'

Hi. I have a java game I made in a course at Uni. It has three Timer objects.
When I run the game from Notepad++ it runs perfectly (sweet-as game if I may say so myself).
I have made executable .jar files so that I can share it with friends. Unfortunately sometimes the game runs 'slow' when run from the .jar.

I have the feeling this has nothing to do with errors in code (due to the randomness of the error's occurence) but rather a runtime problem (if that's the right word..).

Anyone know what the problem might be?
Also plz keep elitism to a minimum

>>33
They're more noticeable when the player is larger. You still have to look for it. It was interesting looking at how you did it though.
Didn't realize they gave you part of the code.
Did you do all of the graphics programming too? That had to be a bitch!

 >>34
Meh, code I was playing around with when I had free time at work. Just giving ideas.