security certificate errors

I am plagued with security certificate error messages and it's getting worse

by the day! I am running Windows XP SP2 with IE 7.0. Some of these messages

indicate the certificate is out of date when they are not. I even got a

security warning when accessing this page to post a new thread.

I am also having a problem downloading a payroll update for my QuickBooks

pro 2008 software. The download appears to proceed and at the very end I get

an internet connection error message which suggests that the date on my

system may be incorrect...it is not. QuickBooks support is of the opinion

that something is blocking their software from making the necessary

connection to finish the update. This problem is fairly recent and started

after I downloaded and installed the latest windows updates. Any chance the

update(s) are the cause of these problems? If not, any idea what could be the

cause?

Thanks,