If there were a problem with AB's Security Certificate, I feel sure other members would have been posting on the matter.
It could be as suggested by treetops....."either your AV is playing up or you may have a nastie on board." Consequently, as an out-of-date Browser can also cause the problem which you have, I am requesting a lot more information.
What browser are you using (Internet Explorer, Firefox or whatever )and the version number. Also what make and model is your Computer/Laptop and the operating system (Windows Vista, W 7 etc) Please also say if you have an Anti Virus programme and what it is, along with whether you have Malewarebytes or anything similar.
I shall be away for the rest of this morning but will look in again when I return home at about 1.30pm.
Hans.