Why must I continually sign-in in order to gain access to MY YAHOO page after choosing "sign in

My Yahoo homepage is continually gone, replaced with the generic page every other time I go to it... I have not deleted cookies or temporary files since "sign(ing) in for two weeks" and accessing the page normally. No changes have been made to my OS or my browser or my ISP or my Yahoo ID or password, nor am I using a different or currently shared pc. I am not behind a firewall, nor am I on a LAN or WAN. I use a 56k modem on a simple twisted-pair, non-dedicated landline. I am not attempting anything involved with remote access. Since I am not admin on this machine, no registry modifications have been made by me or anything I can install; and, effective anti-virus protection is installed, as well as automatic update capability being enabled for the MS WinXP-SP2 OS running. I can use any one of three different browsers: Firefox, Mozilla, or I.E.7; and, I do not make use of a third-party mail client or proxy. It appears that this is a Yahoo SNAFU; and, I am unable to confirm this.

Why must I continually sign-in in order to gain access to MY YAHOO page after choosing "sign in for 2 week"?antivirus programs

In "Internet Options" are your privacy and security settings both set to default? Seems like the cookie is being blocked for some reason.

Why must I continually sign-in in order to gain access to MY YAHOO page after choosing "sign in for 2 week"?computer protection

Do you sign out when done browsing the internet? If so that will override the selection to keep me signed in. Also if you shut down your computer that will do it too. Sometimes the firewall ,antivirus,popup blocker will change the way a computer operats. Also if you have downloaded service pack 2 from MS there have been problems with how the computer operates. Also if you happen to have 2 different antivirus programs or firewall programs conflicts arrise and may even lock you out of your system all together. I know for one that firefox will reset your operating system too, I don't know if mozilla will or not but it's a good bet it will.