I thought I had fixed everything with clicking continue but the problem came back with a vengeance, popping up with many sites besides the s-static.ak.facebook.com.
I eventually did quite a few things and my problem now appears solved.
- I deleted all certificates in Keychain that showed with a red x (not verified)
- I downloaded the latest combo OS 10.6.8 update (my current system) and reinstalled it.
- I reupdated Java and Silverlight
- I ran Onyx maintenance to remove all system and user and web caches, history, and to force spotlight reindexing
- With Onyx, I ran the maintenance scripts and repaired permissions
- I did a full antivirus scan with Sophos (nothing found)
- I waited overnight.
Like another user before, I am not sure what step actually solved the problem but everything seems finally OK.
Good luck.