You can try to download it from Apple website from apple.com/safari
Did you get an error when trying to download it from the Software Update?
Did you repair permissions before downloading the update?
Ferruco do you have OnyX. If you don't get it here http://www.titanium.free.fr/pgs/english.html . If you do then go to automation and run pretty much everything there. It will take a while . But it may just do the trick. I had something similar a while back and cleaning the caches running the automation script seem to help a lot. Good luck
I second Onyx. It's a must have app on Mac. I rarely have my computer running at night so all those maintenance scripts never run without Onyx. It definitely takes a while to run it but very worth it.