Greetings,
Are you still using Safari 4.0 as your profile states, or have you updated to 4.0.3?
As for your problem, try this:
1. Go to Home/Library/Cookies and delete the Cookies.plist file.
2. Go to Home/Library/Caches/com.apple.Safari and delete the contents of that folder.
3. Go to Home/Library/Caches/com.apple.Safari/Web Page Previews and delete the contents of that folder.
4. If you don't want to use the Top Sites feature, open Terminal and paste in this command:
defaults write com.apple.Safari DebugSnapshotsUpdatePolicy -int 2
5. Go to Home/Library/Caches/Metadata/Safari and delete the contents of that folder.
6. Go to Home/Library/Caches/Safari and delete the contents of that folder.
7. Go to Home/Library/Safari and delete these files (if you have them):
Downloads.plist
History.plist
Form Values
LastSession.plist
WebpageIcons.db
Then restart Safari and see if the problem continues.