Hi Krish and welcome to the forums.
The obvious question will be, "were you making any configuration changes when the browser hung?".
Additionally, is the VPN router still reachable? Can you ping the public interface (assuming you are allowing ICMP ping)? Is the VPN router still working properly in terms of user traffic?
I've seen the Nortel VPN router core and reboot sometimes making various configuration changes but I've never seen it hang and web server. If you have SSH or a modem attached to the console port you could try remotely rebooting the device. You could also have someone power cycle it for you.
Perhaps you are using the wrong URL or port? Were you utilizing SSL to connect (https://) perhaps you were using port 10443 as opposed to port 443? (
https://vpnrouter:10443)?
What version of software are you running?
I've generally not seen any similar issues with the 20 or so Contivity 1010,1050,1100,1700,1740 models that we have installed.
Good Luck!
Good Luck