SLES 11 Switch user problem

Hi,
I am using
SUSE Linux Enterprise Server 11 (x86_64), PATCHLEVEL = 0 as NIS server.
All client is having SUSE Linux Enterprise Desktop 11 (x86_64), PATCHLEVEL = 0.
All system are configured to work in GUI.
When NIS user say 'a' locks system, and user 'b' wants to login to the same system he uses switch user option, but user 'b' is not able to login and screen returns to lock position.
Is it a bug in SLES 11?.
Please help.

This subforum is not intended for technical questions - I move your thread to the SuSE area.