We have updated our version of php so the default used is PHP5 rather than PHP4. This can cause the error message "product not found" when clicking on a product in OSCommerce
This problem is caused by the fact that PHP 5 has "register_long_arrays" set to "Off".
To re-enable it add the following line to a php.ini file in the root directory of your site.
register_long_arrays = On
If you site already has a php.ini file, just add it to the next line in the file.