If Windows XP, it's usually that the root store is corrupt [1]. Otherwise it's usually a bad system clock. If nothing else, see chrome://net-internals and you can repo the problem and find the SSL socket under "Events" to see the actual chain and error code.<p>[1] <a href="http://www.microsoft.com/en-us/download/details.aspx?id=35945" rel="nofollow">http://www.microsoft.com/en-us/download/details.aspx?id=3594...</a>