User Authentication problem after Update to 9.1.x

We are experiencing a problem with a handful of users who are unable to authenticate to the Thin Client after upgrade to 9.x from 8.6.x. The user continually receives a bad username\password message when trying to login to the client. This problem follows them to other Thin Clients. Our work around has been to give them a laptop.

We have about 5 users out of 900 that are experiencing this problem.

Wyse 3040 running 9.1.x all versions