When you enable the feature "Search Engine Friendly URLs" in Joomla 1.5, your articles may show incorrectly with PHP 5.2.

The best way to resolve this is:

1. Rename the file htaccess.txt to .htaccess in your Joomla's root directory;

2. Set to "Yes" the feature "Use Apache mod_rewrite" in the SEO Settings

Alternatively you can downgrade your PHP version to 5.0 and the problem will be also solved.