Hello. I too have a problem with getting a solid image from my 1040STe. I only use monochrome mode to VGA monitors.
I have tried two separate VGA cables and multiple CRT/LCD monitors, and the problem is always the same.
On boot-up, the monitor will "auto adjust" to the image. And it will look pretty solid for approx 10 minutes. Then the vertical banding/flickering becomes progressively more noticeable until it is just annoying. Asking the monitor to "auto adjust" again will fix the problem for a time, but it will revert back to the problem just the same as before.
Both the VGA cables I have allow for sound and color options and I was wondering if "interference" might have something to do with it.
Would a strictly "monochrome/no audio" cable help my situation? I really don't want to spend another $30 on a VGA cable, but my soldering skills are quite novice.