Any idea why when I create shapes with the marquee tool, some edges will either be faint, or non existent? Yet When dragging the shapes around with the cursor, the edges will become visible again while others will disappear. This has never happened before. I'm using CS3. The same happens when I use the pen tool, rounded rectangle tool, polygonal lasso etc.
How do you have your anti-aliasing set up? That can be a big part of it as can the scale you work at (ie: 66% or 50% vs. 100%). Photoshop will feather the edges of the marquee if you set it up that way. Double-check your preferences.