Security Certificate errors

[ItsRobsLife]

The last couple of days I've had Firefox blocking a lot sites due to security certificate errors, basiclly saying that security certificate is not up to date and cannot be trusted. The sites include my Gmail account and Xbox.com that use https so no real issues there as far as I'm concerned and I've manually allowed access. I've just been trying to log into another site I use and Firefox wouldn't even allow the password prompt box, so I tried it with IE7 and that too is raising a security alert. So I assume then it's not the browser. I've run anti-malware and CCleaner and an AV scan, but everything seems clean, so any ideas what's going on?

[ItsRobsLife]

Certificate will not be valid until (date)

(site name) uses an invalid security certificate. The certificate is not trusted because the issuer certificate has expired. The certificate will not be valid until (date). (Error code: sec_error_expired_issuer_certificate)
This error can occur if your computer clock has the wrong date, in which case the date given in the error message will be in the past. To fix the problem, set your system clock to today's date and time

(double-click the clock icon on the Windows Taskbar)

.

Er.. ok just found the solution to my problem. Always worth asking you guys though.