White pixels incorrectly appearing on canvas

My program simply shows images on the canvas with transitioning effects. Images are loaded up in a separate thread (using ofThread) ahead of time and then placed on the canvas.

As can be seen in the attached image (apologies for the terrible photo) there are some white pixels being incorrectly drawn across the top of the screen from the left. These pixels sometimes flash and sometimes do not. Perhaps importantly they follow the image as it’s moved or resized (grown or shunk).

I’m wondering if perhaps it’s a graphics card issue, as it didn’t happen on another machine but has happened on several other machines for the same codebase. In all cases I’m using Ubuntu 12.04.2 with open frameworks version 0.062.