I posted this in the ANSWERS forum 2 days ago. It seems here is a more appropriate place. Therefore, I am re-posting (with a little bit additional information).

I've registered in knowledgesutra for several months (Username tsangsir). I've not been able to stay signed in the forum. After sign in, I was kicked out in several page clicks, There is no message. It's just like I have never logged in or clicked sign out manually. I clicked frequently (< 1 min interval) so that there should be no timeout. Using different options in the "remember me" checkbox on the sign in page made no difference. Any idea on what's wrong? I have enabled cookies.

The same issue also occur with astahost. I could not test recently because it have no response.

Seems no one sees this... Anyway, here are some updates

1) I set up facebook connect. The same problem occurred.

2) Actually, it seems some page will kick me out in 100% of attempts, others seems more random. For example, the Post Reply page and Profile -> (any links) kicked me out 100%

3) By using sites like http://www.whatismyip.com, it's found that my every web access has a different IP address. These IP addresses are different from the IP address the ISP's DHCP assigned to my own computer. Is this a cause of the issue?