Pogo certificate error

[lucky9999]

Does anyone know what might be causing a error message when I go to sign into pogo?  It says the certificate for this site is not valid and you shouldn't use the site.  I have contacted pogo about this, my ISP provider, my anti virus program, ran the advance system and still can't fix this.  Pogo said it was a corrupt java so I unistalled and re-installed and no change.
In talking with Pogo again they said to use Chrome which is giving me the same message except with a red screen.  They said that I am missing an add on and I should check another browser to see what add ons that one has.
My anti virus program said did have to go in and unistall and make some changes to Internet Explorer but I don't know what changes they made and they said to contact the computer company for help.  The warranty has expired and they want to charge me per minute.
Was just wondering if anyone had this before or has any suggestions as to how this might be fixed.
I have windows xp, with explorer 8.  Can In tenet Explorer be totally removed and re-installed and if so how is that done? 
Help section in Internet Explorer questions is of no help so thought I would try here.
I would appreciate any and all suggestions or help. 
Thank you

[C~M]

it doesn't mean the site is unsafe, it just means they haven't paid for or renewed their certificate which proves they are safe, you can still go to the site and play.

[lucky9999]

it doesn't mean the site is unsafe, it just means they haven't paid for or renewed their certificate which proves they are safe, you can still go to the site and play.

Ok thank you!!!
I was just wondering because I am not having that problem with firefox or sea monkey.
Thank you again.

[Darling SilverDodger]

This might help.. check your clock.. I get that message when my clock  was with the wrong time