Could not create directory with // during module install

During initial enable of Plugin Manager module on Drupal 6.9 ( Apache/2.2.3 (Ubuntu) mod_fastcgi/2.4.2 PHP/5.2.1 mod_ssl/2.2.3 OpenSSL/0.9.8c mod_perl/2.0.2 Perl/v5.8.8 ), Drupal Modules page showed an error: "/home/www/sample.org/public_html//sites/all/themes". There are two consecutive slashes between public_html and sites in the error message. Making the directory by hand (with only one slash) seems to have resolved the problem.