SMF Forum losing session immediately, happens in all browsers

This is a really strange issue and not directly "programming" but I'm hoping this is an okay place to ask.

Basically I have a user on the forums I run where they basically log in and are immediately being shown the public forums only. The forums are updating the "last login" field for this user so authentication is working fine. The really strange part that might also in开发者_如何学编程dicate the problem is that this issue occurs in IE, Firefox, and Chrome.

The user has tried other accounts and the same problem happens -- but when using another computer in the same house (same network), everything worked fine.

I'm sorta' stumped on what could cause this when it applies across all browsers.

Their computer isn't accepting cookies. SMF holds it's session data in the cookie. It will use the db to keep track of who's online, so they might appear on the list but without the cookie the session is over