I have noticed since you upgraded the site that more often that not when I hit the back arrow I get this. Seems to happen when I do an ip search and clicking on linked Guids and then going back to click on another one.
Webpage has expired
Most likely cause:
The local copy of this webpage is out of date, and the website requires that you download it again.
Something to try:
Click on the Refresh button on the toolbar to reload the page. After refreshing, you might need to navigate to the specific webpage again, or re-enter information.