Problem with serialization of data

[eluser]vikascoollives[/eluser]
I have created permissions for each function for different roles , i.e users are categorize as per role assigned and permissions are given as per roles .

I store permissions in session as the user logged in. But first I serialize the permission array and unserialize before checking the permissions in controller function . But I am facing problem in some cases like where a took more time to fill the forms .

otherwise it works fine for me . Can anybody suggest what i did wrong ?