One of the goals for Joomla! 1.5.4 was to build consistency for Joomla! Component Page Titles for each of core template. Overall, the project was very successful except for the appearance of "double titles" on the Article Layout due to both the Page Title and the Article Title printing on the Web page. The reason for this quick release of Joomla! 1.5.5 is to resolve this problem.

Page Titles will appear on Articles only if each of the following three conditions are true:
Articles that are navigated to by clicking the "Read more..." from a Blog, or clicking an Article Title from a List, no longer print the parent Page Title on the Article Web page.
As a reminder: the "Show Article Title" Global, Menu Item, and Article parameters continue to govern the display of the Article Title. That did not change with the Page Title consistency work and it has not changed with this fix, either.
Thank you to the Joomla! community for your patience and support, for helping one another, and for testing the patch to ensure it resolved this problem.