[eluser]WanWizard[/eluser]
That is not "fixed". That is worked around.
If native sessions work, that only means that PHP's default config of the cookie parameters is better than yours. In the end, ALL session solutions work the same way.
Configure the session and cookie parameters properly, and switch back to CI's session class. It's more secure.
When you hit an issue, debug it, and fix the problem. Working around it leads to sloppy code.