I'm not sure if this has been asked before or if it is a common problem so i'll just tell you whats up and hopefully someone will know whats going on.
Basically, i have only been using photoshop for a couple of days, i'm getting ok at it now, have made a couple of cigs and made a few pics look funky, but then in the last hour or so, things have started going weird.
I opened a new screen and set a black/green gradient on the picture. I then applied a wave distortion to it (as i was following a tutorial). Once i'd clicked apply, the waves came through but also what i can only describe as random white pixels dotted around the black parts of my picture. They can be blacked out or erased but then just move about to another part of the picture.
Personally i find this very weird, but hopefully there is a simple explanation to this problem and it is just some option i have changed or something.
I can make a couple of screenshots of before and after if that helps.