I have installed wampstack-5.6.18-0
Before making any changes, I'm able to launch phpmyadmin with no problems.
If I uncomment the following line in wampstack-5.6.18-0\apache2\conf\httpd.conf
and remove the sample virtual hosts form \extra\httpd-vhosts.conf to leave it blank, I am able to launch phpmyadmin just fine.
As soon as I add a vhost, I get a 404 The requested URL /phpmyadmin/ was not found on this server. but my vhosts all work.
If I comment out the vhosts again, phpmyadmin launches.
If I add a new vhost for phpmyadmin I get a 403 Forbidden You don't have permission to access / on this server when trying to access the phpmyadmin vhost