Bruins Mom

I am trying to log on to my local High School Districts online gradebook
site, and I keep getting a notice that the websites certificate has been
revoked. I have never had this problem on my old computer (prior to Vista)
and my sister-in-law (whose computer does not have Vista on it) can still
access the same site with no problems. This is very confusing and
frustrating!!!
Can someone please help me???