Could you copy/paste the command and output that you are using
Seems to me its a Question from internert, can you show us the result here what you type and what you get.
Hi Sir, it's not a question from the internet, the error really occured in my environment , see below the output ,
SQL> conn system/manager;
ORA-24315: illegal attribute type
Warning: You are no longer connected to ORACLE.
my Oracle version 10.2.0.1.0 , Operating System RHEL 5
What if you try this
$ sqlplus system/manager
Hi Sir, The problem was resolved atlast, by connecting the user through help of Enterprise Manager and by locking and unlocking the 'system' user. being as 'sys' user., and keep on logging as system user. 2 -3 times.,