Look at the page source (HTML) View > Page Source. Is your missing code contents there? If so, start looking at the CSS to see the font and foreground and background colors. If you have FF, install Firebug to examine the code section source. If you add more lines to the code block, does it grow (but empty), or is it empty period? If the page source shows nothing within the code block, that would be very strange. By any chance do you have any odd characters at the beginning of the code, perhaps something that's a control code? You can try a line of "code" like "Hello, World" typed in, not pasted in.