Thanks for the reply Jhynds.
The issue we are facing is since we had LEM version 6.3HF7. We did raise ticket with support but unfortunately we didn't get much out of it we also had WebEx session for that in which we were advised to check logs of windows machine as support was sure that it is windows OS causing the Signout issue.
We were unable to get anything out of windows logs which could point out exact error.
I guess we have to reopen the ticket and check if this time we can find a solution.