Getting exception while modifying existing user

[mohan]

Getting below exception when trying to modify the existing user .please help

[jllort]

Which openkm version are you using ?. About user modification, you're modifiying from Tools -> Preferences -> User configuration ?
Which kind of change you've done ?

[mohan]

I am using OpenKM 6.2.3 Tomcat bundle.

Under Tools->preferences->user configuration looks like attached screen shot.
Here i want to add user to one more role.

[jllort]

No no no, here is not the place to change user roles, that can only be made by administrator in user administration view , take a look here http://wiki.openkm.com/index.php/User_administration