Auf einem 7er Server brauchst Du auch eine 7er Resourcen DB, ansonsten kann das auftreten, was Du geschildert hast.
Es gibt hierzu folgende Technote:
Title: Resource Reservation databases based on 6.x or earlier design do not function properly on Domino 7.0 servers
Doc Number: 1219243
Problem:
Resource Reservation databases (RRDB) based on a 6.x or earlier design do not function properly on Domino 7 servers. Overbooking of rooms and resources can easily occur if you attempt to use a pre-Domino 7 RRDB on a 7.0 server. For example:
Rooms requested through users' calendars will not be booked, and no notifications are sent.
Reservations booked directly in the RRDB will appear to have processed; however, busytime is not updated.
Cause:
The Domino 7 Rooms and Resource Manager task (RnRMgr) is designed to handle the processing of reservations in the RRDB, including handling all notifications, autoprocessing, and the updating of room- and resource-related busytime records. The Domino 7 mail router was optimized to allow the RnRMgr task to function correctly by removing the logic associated with the autoprocessing of room and resource requests.
The Domino 7 Schedule Manager task (Sched), which is responsible for updating busytime for mail databases, was updated to not monitor any RRDBs. This means that any directly created reservation requests will appear to have properly processed; however, busytime is not actually updated. And as a result, rooms and resources can be double booked.
Therefore, because Domino 5.x and 6.x RRDBs require the legacy router and sched tasks in order to operate as designed, they will not work once your server is upgraded to Domino 7.0.
Solution:
Lotus Domino 7.0 is working as designed. To function correctly on a Domino 7 server, the Resource Reservation database must be based on the Domino 7 Resource Reservation template (RESRC7.NTF) For the best results, the design of this database must be upgraded at the same time you upgrade the server to 7.0.