Thanks lat9. I've tried that but unfortunately still get the blank pages.

In either case I get the following errors in the logs:

Accessing the Admin:

Code:
PHP Warning:  session_start() [<a href='function.session-start'>function.session-start</a>]: Cannot send session cookie - headers already sent by (output started at /home/thai1/public_html/test/MYADMIN/includes/classes/logger.php:127) in /home/thai1/public_html/test/includes/functions/sessions.php on line 113

PHP Warning:  session_start() [<a href='function.session-start'>function.session-start</a>]: Cannot send session cache limiter - headers already sent (output started at /home/thai1/public_html/test/MYADMIN/includes/classes/logger.php:127) in /home/thai1/public_html/test/includes/functions/sessions.php on line 113

PHP Warning:  Cannot modify header information - headers already sent by (output started at /home/thai1/public_html/test/MYADMIN/includes/classes/logger.php:127) in /home/thai1/public_html/test/MYADMIN/includes/init_includes/init_templates.php on line 55
Accessing the Catalog:

Code:
PHP Warning:  require(DIR_WS_TEMPLATEStemplate_default/common/html_header.php) [<a href='function.require'>function.require</a>]: failed to open stream: No such file or directory in /home/thai1/public_html/test/index.php on line 85

PHP Warning:  require(DIR_WS_TEMPLATEStemplate_default/common/html_header.php) [<a href='function.require'>function.require</a>]: failed to open stream: No such file or directory in /home/thai1/public_html/test/index.php on line 85

PHP Fatal error:  require() [<a href='function.require'>function.require</a>]: Failed opening required 'DIR_WS_TEMPLATEStemplate_default/common/html_header.php' (include_path='.:/usr/lib/php:/usr/local/lib/php') in /home/thai1/public_html/test/index.php on line 85