[qualiteam]

"DirectoryIndex cart.php" makes the server to load the X-Cart's front controller when a visitor opens your domain - this should not trigger any error unless you have some specific server setup.

What is blog.xxx.com.my? Would you like to install Wordpress to this subdomain, and keep X-Cart installed at xxx.com.my? If so, the server should route these domains into different web directories on the server.