Hi Hasan,
Not quite sure what is going on here.
I created a LE and while tryng to add it to the ledger, I got this error as attached.
Regards

Usually we get this error when we try to do the navigation using browser's back and forward button. Also when we open multiple sessions. However some times we do get this message due to defects.
Having said that you need to rule out if this is a temporary glitch or not. Close all sessions of your IE browser and try sign in again. Try adding the legal entity again to the ledger.

Hi Hasan,
None of those approaches could resolve the issue.
I believe it's a glitch on the system. However, you can ignore the issue as I have alternative to achieve same result.
Regards

Sorry for the late reply.
If restarting the system is not solving the problem then it is not a temporary glitch. There is no quick fix as well. Recompiling the flexfield would be the n ext step to see if that is fixing the issue. If not then the form needs to be recompiled and so on. In an production environment one would open a ticket with Oracle for such issues. If you have alternatives then you might not want to spend time troubleshooting the issue.