I imagine this thread is dead given the date of last posting, but the error message pookie & mester are getting to me would imply a Network Access policy for the non storage of passwords or credentials has been enabled. Disabling that policy would likely sort this issue.
Alternately, they could press the windows key once then type credential manager into Cortana's search box and press Enter key, then scroll the list of credentials and delete the one related to the activity they are attempting to perform when the error occurs, i.e. in the case of the OT post, delete the credential related to Solitaire, and the case of mester, delete the credential related to signing into their x-box account.