Hi Robert,
Thanks for the reply.
I got the error in the symbol editor only.
I tried to edit one symbol by using symbol editor. I can't select the add pins button(because button disabled). But i can move pins and edit the available pins. If i add one more pin by using copy and paste means i got "the symbol has frozen interface".
I don't know how to unfreeze the symbol and edit....
Regards,
Sajiv.