The file logo.jpg is in the same directory as the cgi script

Actually, the way you've written it, I think 'logo.jpg' needs to be in the cwd (current working directory) which is not necessarily the same directory as the cgi script. You could modify the script to 'use Cwd;' and 'print getcwd();' so that you can check on just which directory is the cwd.

What happens if you specify the full path to logo.jpg in the script ?

Cheers,
Rob