Hello generous support forum viewers! This morning one of my users told me she couldn't get on to our Inventory system, which is hosted on a SharePoint 2010 site. I checked she was using FF v41. I go back to my machine, check that I have v40.? installed, and it notifies me of update.* Before running update, I check that I can get into our Inventory site and it loads with no problems on v40 I run the update, restart browser, and it can no longer open our Inventory site like it always used to. I get error message from SharePoint, "The Form 'inventory%20nav' is not available. Click here to try again." No error msg from FF. For now, I have recommended to my users to use Internet Exploder for our Inventory site and nothing else. It seems there was a change in how the engine renders web pages in v41? I can do limited testing in my environment if someone has beta packages to send me, but our whole shop is swamped, so I won't be able to spend all day on it, just maybe an hour or two. * = I think it was v40.3 btw this is FF on Windows 8.1 with only 'Important' updates applied, SharePoint 2010 hosted by Server 2008 R2 and Microsoft SQL 2008 with most updates applied, but there may be a few very recent ones we don't got yet.