Have you tried logging in to a test user account to see whether your issues follow you? (If you haven't already got one you can create one in /Apps/Sys Prefs > Accounts.)
Have you tried a browser other than Safari?
Have you considered updating your Safari installation? (You can get to v 5.0.5 by simply running
the Mac OS X 10.6.8 Update Combo v1.1, and from there you can get to v 5.1 with
this standalone d/l.)