I currently have multiple workstations receiving this error when attempting to login. I have also noticed that if I try to change the settings of one of the affected users in ConsoleOne, it gives me an error message there as well.

Novell Client Error - internal error 0x00008960 occurred
ConsoleOne Error - Error -608 (An attempt was made to add a property that is illegal to an object)

This is the Novell Client 4.91 SP5 running on Windows XP Pro.