I have a strange horizontal streak in my Hp 24 inch LP2465 monitor using the DVI cable. And for the life of me I cannot figure out what is wrong. When I first built the PC in Feb 2009. But for last few months the streak has emerged.
Are you sending an analog signal instead of a digital signal from the Lenovo T61p? The DB-15 port on the T61p is analog only which explains the difference in response by the monitor to the input signal.
I'd bet money it's a monitor problem. When you get defective rows of pixels that never move, it's usually an internal problem. A bad DVI/VGA/HDMI cable wouldn't cause a set row of pixels to not work. The way data is streamed in DVI and HDMI, if you lost a data line or a clock line, it wouldn't do anything like that. If you lost a color line or a vsync / hsync line in a VGA cable, it does nothing like that either.