GD Image Loads And Then You See White Line Go From Top To Bottom of Pic - Why?

[phpQuestioner]

i have a gd image that loads and once it is clicked a pop-up will open and display the image again only at a bigger size. i am not resizing the image with gd; i am resizing with regular html image tag's width and height properties. when the initial gd image loads for the first time; it loads normally, but when it loads in the pop-up window; it loads normally and then it is like it reloads itself again, because you can see a white line go from top to bottom of the image. i do not know what is causing this; i was wondering if the gd image is being cached by the browser and displays at first; then the gd code loads from the php script and the white line is because the background of the pop-up is white and the cached image is being reloaded from the php script.

 

any way - anyone have any ideas? - anyone know how to prevent this? - would i us a no-cache header?

 

if anyone has had this to happen to them or knows of a quick fix; please let me know - thanks.