I had reset my AC68U several times after the update to firmware 454 due to AC68U hanging with switch hardware acceleration enabled. Most of you had not encountered this issue with your AC68U with firmware 454.
I had discovered that AC68U will hang after I setup a IPv6 Tunnel (6in4) via tunnelbrokers.net with hardware acceleration enabled. If I disable hardware acceleration, everything works fine.
I further discover that on my setup, with WAN DoS protection enabled, the AC68U UI will be very sluggish. If WAN DoS protection is disabled (default), than the UI is snappy. This is with Chrome browser.