I am also seeing this situation, in my case users who normally can log in fine suddently can't, with the error you noted. At times, I get eh same error accessing the CMC. I have found that once the error starts appearing, it is necessary for the affected user to restart their browser before it will clear. Also, if you can get into the CMC, going into the AD Authentication and clicking the update button will clear it up.
I have not figured out why this randomly shows up.
Rich Walker