Same thing happens to me if I quit out of a game via the XMB on my 27 inch little cheap LCD. I wouldn't worry about it man, i think its what you said just like some refreshing or just a screen that comes up while the PS3 is figuring out what its doing and switching modes from gaming to the XMB or whatever.
PSN ID= bigdaddymoo
MSI GT725-074 owner..... TRUE BEAST.. COD4 is a different game on PC.