I have also noticed in the logs (messages) that DHCP is restarting often and reissuing new leases to the workstations.
I've also updated my server to 7.1.1, and smeserver-openvpn-bridge-fws is still working (even if I have some others problems with the server-manager).
If DHCP is always restarting, you should:
- verify that the internal interface set in openvpn (via the panel-> advanced page) is eth0, I know some strange situations where openvpn think the internal interface is br0 (this occure when upgrding openvpn when the old version is still running, it's quite starnge because the new rpm should stop it before the installation)
- restart openvpn (from the panel or from the command line /etc/init.d/openvpn-bridge restart), and have a look at the log