Safari and Software Update can't connect to internet, but Firefox can

I installed all suggested updates yesterday and this morning Safari, iTunes and Software Update can't connect to the internet BUT FIREFOX HAS NO PROBLEM.
I ran Network Diagnostics and it says my connection works perfectly.
I checked the proxies, it's on auto discovery, seems alright to me.
I checked the DNS, and changed them several times, nothing works there...
I verified every forum, no good answer.
I'm not a pro but if anyone has a suggestion, i'd be very grateful.
I'm now trying to uninstall and re-download safari 5.0.3 again see if it's a miracle...

-Intel Macbook running OS 10.6.5

Thanks!

yes for Little Snitch, always, and it doesn't show Safari at all on the network monitor even when i try to open it...

i'll check the permissions right away

Repaired permissions on HD, still doesn't work... (there was a lot to repair though), everything was fine (connections, permissions etc.) before I installed the 10.6.5 combo update issued nov. 10.
Little snitch is not the problem, it's the first thing I checked.
Software Update and iTunes, and now iWeb are affected also. Seems all native Apple software are affected. Firefox, uTorrent are able to connect without problems.

I sould've tried this before.
Brought my computer elsewhere and everything worked fine. So it has to do with my home network; i'm not that good with this.
Makes sense since all native Apple apps use Network Pref setting to access to the internet (proxies, DNS ...)
but Firefox, uTorrent etc. have their own settings.
Disabled Auto Proxy, didn't change a thing.
Any ideas?

reseted the router and the modem, didn't work either.

I read a whole book on networking (those are useless by the way) and I can't figure out my problem. Seems there are some variant if not similar threads on other forums but none of the very few solutions proposed are working for me.
Tried putting my computer in DMZ on my router cause I thought it might be a firewall problem. No.
Installed every update available. No.
Tried countless times resetting my router, modem and then restarting. No.
Tried changing IPv6 or other then apply. No.
And I don't understand this last post, that guy is lost.
At least I have Firefox for the net and Transmission for downloads.
I should survive just well since everything works anywhere else but here and I have a very portable Macbook after all.
Thanks all for your help.