Same here. I tried deleting the caches.... tried removing and reinstalling silverlight to see if it has anything to do with it- nope. Tried flash player - tried everything - doens't even load its own webpage - www.apple.com. I even tried to remove Safari and do a clean install on safari 5.1 - it turns out the latest verion you can download from the apple website only works for snow leopard - so you can't even re-install Safari (for those who are thinking about reinstalling safari - DON'T remove the program just yet...) I'm starting to think there's nothing we can do (on the consumer level), and we just have to wait for the developers to fix the issues for us.....
Go to ~/Library/Preferences. Move the com.apple.Safari.plist file from the Preferences folder to the Desktop.
Quit then relaunch Safari to test. If that helped, move the .plist file to the Trash.
~ (Tilde) character represents your Home folder.
For LIon: To find the Home folder in OS X Lion, open the Finder, hold the Option key, and choose Go > Library
Or, could be a Safari third party add on that was compatible with SL and the prior version of Safari, but not Safari 5.1
Or... for any sites you have problems accessing...
Go to ~/Library/Cookies. Move the Cookies.plist file to the Trash.
Quit then relaunch Safari. Try Facebook.
Since I just quit my job, I have some free time on my hands -and here's what I did. I ended up have to re-install Lion for the 4th time and this time around, I erased a bunch of apps I had purchased from the App store before I did the total CLEAN install of Lion. After a painful 3 some hours later, Lion was once installed and I had to reset everything again, and interestingly enought this time when i open my Hard disk, there's a folder named "incompatible software" - and it has programs from Smithmicro, and Virusbarrier.bundle, so i know these COULD be the ones that are causing the problems. At any rate, I started my process at 9pm last night and finished everything around 2:30am, and my Safar is fast as a Cheetah (Apple may want to name the next OS X 10.8 this). so Problem solved, but LOTS of work..... I didn't try the suggestion from Carolyn above, but for those who are having the same issue - I sould suggest to try other means first before going down the route that I did (unless you don't mind a lot of work and have a little bit of time on your hands as well.) Hope it helps and good luck ! ( BTW - Timemachine or back up everything before you perform the clean install, my music in iTunes were ok, but all the movies and tv shows were erased, so i had to reload everything again.) Bottom line, i love the clean install - everything starts from beginning and everything seems just a little bit faster........ without all the clutter and old caches.