I just updated to 2.2.1 through the Wordpress plugins updates page on the back end.
As soon as I refreshed my page I now get an IIS 8.5 error page saying that I'm getting an HTTP Error 500.19 - Internal Server Error with the code 0x8007000d meaning that something in my web.config file (apparently some xml) is "not well-formed". I now can't access ANY file front or back end from my domain.
I'm waiting to hear back about FTP access so that I can work on the web.config file but I'm hoping here that someone else had the same problem and know what xml in the web.config needs to be fixed to solve this problem. In the meantime, the site's absolutely useless. Some help ASAP would be very much appreciated!