Just downloaded Processing on a laptop using Windows 7 64bit. This is the very first and basic work that is being done inside of processing itself.
So far, I am trying to re-create the example from the processing tutorial on the site here:
Processing Example.
When doing that simple example my window becomes distorted as soon as I do the following seen in this picture here:

I am completely unsure of why this is happening and sometimes as soon as it does happen, I cannot get it to go away, even after moving the ellipse to another area.
Any ideas?
You have two tabs in there. Unlike in a more traditional IDE, Processing considers all code from all tabs part of the same sketch, so it’ll run all the code you have in those tabs. Not just the size/rect/ellipse calls, but also everything in that “test” tab. Fire up a new instance of Processing and just add the size/rect/ellipse calls (or delete the test tab). If it doesn’t do weird resizing, problem found.