@scottwell : i added this system setting "session_cookie_domain", but still it doesnt works

Below is what all i did,
1) added this setting on both the MODx (sub1 and sub2 aswell) Just to make sure i tried if setting i just created is accessible to MODx...and yes "session_cookie_domain" is fetching the new value.
2) As i have said before i created simple php pages outside MODx...and found that they share session i can see session created on sub1 is accessible on sub2.
3) when i try to do it with login package...it again asks me for login even when i am logged in on sub...i also created same username password on both the domains.
4) without using login package i simply set SESSION with "testing" key and some value...that also dont get shown on sub2 (which works if i do it outside of MODx)
Is it problem with MODx or login system ??