We had the same issue.  The problem was the firmware on the router.  I believe the version with the issue was 1.3.2.02.  I upgraded to 1.4.2.17.  This fixed the issue.  Beware, 1.4.2.17 has a login issue if you use the VLAN option.  You have to have ...

I cannot use version 1.3. It only allows 2 concurrent client easy vpn connections. I would have to revert back to 1.2.1.14

Update to the previous post.   I updated to the Inter VLAN routing to enabled then disabled the option and was able to login to the router.  After rebooting the router, I can no longer login to the router. This is a major issue since I rolled out the...

I had this issue also. Changing the Administrator did not fix the issue for me.  I was able to login to the router using a VLAN with DHCP enabled.  (THANK YOU Gregu!).  I then enabled the inter VLAN routing.  I could then login using the GUI.  I then...