[LOGIN Problem] Using WWW Or Not. Member Complain Logged Out After Login

[sumampouw]

Hi All, Need solution about Login Problem.

Heres the simulations Steps :

1. I Open FireFox

2. Login to ACP. (www.website.com/admincp) -> Login Success as Admin.

3. Open New Tab For Forum. (www.website.com/forum.php) -> Still Logged As Admin

4. Open New Tab For Forum Again. (http://website.com/forum.php) -> Logged Out.

In Step #4, I can Login again with Another Member (Not Admin) User ID.
And as long as not using www, This ID still Logged In.

But Step #2 and #3, Still Logged in As Admin.

Now there are 2 ID Logged in.

When, I Log out Step #3, Step #2 automatically logged out too...


Is this a normal situation ? (If no, what should i do ?)

Please your input with this case...

Thanks In Advance

This is my configuration :

Site Name / URL / Contact Details

Forum URL        = http://website.com
HomePage URL = http://website.com

Cookies and HTTP Header Options

Session Timeout = 900

Path to Save Cookies
Suggested Settings = / 
Custom Setting = Empty

Cookie Domain

Suggested Settings = blank
Custom Setting = Empty