How can I update logged in user's UserInfo?

Is there any way to update current user's UserInfo?

Suppose a user registered with an email and password,I have customized the CMS_User and added field as MyCV which is a GUID type.Upon logged in,I am trying to upload a file but when the code hits update,it always results in exception.As the user is already logged in and if we try to change the UserInfo,the code might be unstable but is there any workaround in that particular case.

I have tried creating another object of the UserInfo but still gave the same exception.

UserInfo updateUser = UserInfoProvider.GetUserInfo(CurrentUser);
    if (updateUser != null)
    {
        // Update the properties
        updateUser.FullName = updateUser.FullName.ToLower();
        // My Other Code

        // Save the changes
        **UserInfoProvider.SetUserInfo(updateUser);** *//Exception Occurs*

        return true;
     }