I have 2 RVS4000 VPN routers. Neither would accept firmware updates via the admin browser interface using Internet Explorer 8.0. After lots of troubleshooting, I tried Chrome (Google) on 1 router and Mozilla Firefox on the other. Both updates were successful. The firmware rescue utility that you can download from the Cisco web site also works. It does the update without the browser interface, but installs a slightly older version of firmware than is availble for browser-based firmware updates. I hope this saves you time and frustration when you need to update your routers.