We've got a 2830 as below

Model Name : Vigor2830
Firmware Version : 3.6.7.2_sb_232201
Build Date/Time : Jul 8 2014 16:03:51

Connected to a network with SBS2008 as a server. We need 443 open to allow idevices, Outlook etc to connect to exchange when away from the LAN. All is well until I open port 443 to the server ip address. Suddenly we get massive latency and out broadband becomes unusable. Close port 443 and all is good again.

The server works with out issue and is patched up to date,
I have disabled SSL VPN on the router and changed the default port just in case.
I've flashed the firmware and changed the modem codes but nothing seems to help.
I've disabled DOS, no change.
The image shows the green as latency until I close port 443 @ 7am then normal until just before 10 when I open it again.

Any ideas would be appreciated please.

Simon.