I downloaded a free theme and copied it to my themes directory on my server. In my WordPress admin screen, I see the theme name, screenshot, and description, and if I click it, it selects it properly.
Then I began to modify the theme. I changed one image used in the header (same name and location), and a few style parameters. I gave the enclosing folder a new name, and uploaded it to the themes directory. When accessing the Presentation > Themes, the theme is there, but it shows only as the first few lines of text from the stylesheet, not the title, screenshot, and description. If I click this text, it selects the theme, but continues to show the content of the stylesheet rather than the title, screenshot and description.
I've done a side-by-side comparison of the CSS files, and cannot find the problem. Can anyone help me resolve this?