I upgraded a client site to 1.4.1.6 two days ago. All seemed well initally and I was able to update the site content. The next day site users complained that they couldn't make any updates to the content. When I log in as Admin I am also unable to make updates now. I get the following message:
Cross site request forgery blocked
This was initially happening on the User section but now is also happening in albums too.
I upgraded another site on the same host server last week and as far as I know it has not encountered this problem.
Thanks

Try to clear cookies in the browser and re-log in. Also clear the browser cache. If that does not work, please tell from what version you upgraded.