Unless you typed an Administrator password to install something bad, then the problem almost surely is in your account not with you Safari install. You can verify this by creating a new user account. Then use Safari in the new user account. Do you still have the same issue?
If the answer is you still have the same issue in another user account, then the answer gets a whole lot more complicated. If the answer is the problem doesn't exist in a new user account, then you can work on blowing away your Settings and Safari cache in your 'bad' user account.
Report back with your experience after creating a new account.