Try refreshing your cache, one of you still has an old version of the game loaded.
No, refreshing your cache doesn't erase history, but deleting cookies will! On most browsers, open the page and use ctrl-R or F5 or clicking the refresh toolbar button.
You may need to use control-F5 (or control-click the refresh button) on chrome to really force a refresh. All this is doing is discarding all scripts and page data, and pulling a new copy from the server. Your cookies will still be sent to the server and used, so your history will stick.