Here recently my Dell monitor (that's plugged in via vga cable with a DVI converter on it) has been having a wavey signal. It kinda hard to discribe, and it's not always happening. This "wavey signal" is usually occuring on the edges of things ect ect. I recently removed the graphics card in this dell computer that the monitor is plugged into and placed it back in, and everything seems snug fit. What is causing this "wavey" type signal in my montior?