Interesting...my 540c does not look the way you've described. It could be that there were multiple screen vendors, so what you're seeing could very well be normal. I just haven't looked at enough 540s to say. Since your display functions well otherwise, it probably is normal.

The screen on my 540c has dark vertical stripes (very narrow), and barely visible horizontal ones. I assume that these are routing channels for the pixel transistors. It's easy to imagine that some other panel supplier used a somewhat different layout, leading to more noticeable routing channels. But that's just a guess.