I have heard exactly the same experience before. This has an explanation. It is called perceptual adaptation. When we expouse for long periods of time to certain parttern or visual distortion, we can experience some type of after effect.
What I am trying to do with my research is to explain this type of experiences. Since sometimes the GTP experiences are missinterpretated.
I hope you can help me in my PhD project. I will publish the result at my blog.
www.gametransferphenomena.com/survey.html