I am having the same problem but with FTM 2010. Like you, it just started on Friday. Like you, it works fine for Ancestry.com but same authentication error on FTM. I have both a lap top and desk top and both are having the same problem. I've been checking this board since Friday to see if anyone else would have the same problem. I and others had the same problem back in the end of Nov. beginning of Dec. of last year and Ancestry did fix it but it took several days.
So, unfortunately, I have no solutions but hopefully Ancestry will get it resolved before too long.
PS I've also just sent an e-mail to Ancestry Support about the problem and mentioning the Nov/Dec similar problem. I assume you saw the canned response about how busy they are... It might be a while.