Joomla 1.5+ Virtuemart 1.14, got 500 internal server error on any page with a VM element and got core dumps. After experiments, found that the possible reason maybe is that the modified joomla index.php conflicts with VM’s request for index.php and/or index2.php. My site uses a multiple subsites with wildcard subdomain structure and we modified the index.php file to direct visitors from different country subdomains to corresponding country home page, and then direct vistors from the country home page to corresponding city subsites (using wild card subdomains). When replaced the modified index.php with original joomla index.php, the VM can basically work normally without 500 error, but still got minor problems checkout etc. due to the existing multiple sites structure.
Need modification of VM to let it run normally under this multiple site with wildcard subdomains structure.