Hi -
Here is something to check ... I am running MPE 1.2, not the VT variety. Start your 1st adhoc webconf from CUPC between station A and B. Prior to attempting another, from your MPE server, go to Reports and select In-session monitoring. You can also run the Port Utilization report to see the number and type of ports in use. It would be interesting to see how many web sessions are really in use. Also, from the troubleshooting guide, check out this link -
http://www.cisco.com/en/US/docs/voice_ip_comm/cupc/1_2/english/troubleshooting/guide/trouble.html
"Web Conferencing Server Has Reached Its Licensed Capacity
Problem The user receives the message "The web conferencing server has reached its licensed capacity for the current time. Please try your meeting again later."
Solution Buy more licenses, or change the Cisco Unified MeetingPlace Express web floater ports or web overbook ports settings or both. For details, see the administrator configuration and maintenance guide for Cisco Unified MeetingPlace Express at this URL:
http://www.cisco.com/en/US/products/ps6533/prod_maintenance_guides_list.html
Ginger