Safari closes when I open certain pages??

There are a few pages that when opened just cause Safari to close. One is where you have to accept the certificate from an "Not Trusted" site. It is a safe site, yet when I hit accept Safari closes. 2nd site is a hospital page that you need to hit "I agree" to get on the wi-fi. 3rd is a site that I need to get on to check my work schedule (fire dept). All of these worked up until I updated to iOS4. Same thing happened on my 3GS and now my 4. What could cause this? I have played with the Safari settings, but no luck.