Networking - No Internet - Cannot Connect to the Server

Question

I have an old Intel Mac Mini running Leopard (10.5.8, I think) and connected to a wifi network created by a Time Capsule connected to a DSL router.  I use the Mini (connected to a widescreen TV) mostly as a media center for Hulu, Netflix, iTunes, and iPhoto.  The wifi network works fine for my laptop and iPhone, etc., but for some time now neither Safari nor Software Update has been able to access the internet from the Mac Mini.  Instead I get a message that 'Safari cannot connect to [the URL] because Safari cannot connect to the server', and a recommendation to check my internet connection and try again.  But I appear to be connected to my wifi network, Network Diagnostics says my internet connection appears to be working normally, and--most important--iTunes DOES connect to the internet to download podcasts etc. without any problems.  I went to Network Preferences > Security > Firewall and found that iTunes was set to allow connections while Safari was set to block them--but authorizing Safari to allow connections didn't fix the problem even after a restart.  (Also, because Software Update doesn't show up in Applications or Utilities, there doesn't seem to be any way to select Software Update under the firewall, which is understandable but also suggests that the problem is elsewhere.)   So I turned the firewall off entirely and restarted but that didn't help either.  Does anyone have any idea what to do?  Thanks.

Answer 1

Camelot-
Thanks.  I see it but I don't know what it means:  The pane is set to configure proxies manually (the only other option is to configure using a PAD file).  There nothing checked under 'Select a protocol to configure' and nothing entered in the 'FTP Proxy Server' box.  In the 'Bypass proxy settings for these Hosts and Domains' box there are two entries (separated by commas) for '*.local' and 'nnn.nnn/nn' (with the n's representing numbers).  The 'Use Passive FTP Mode (PASV)' checkbox is checked.  Does anything here sound problematic, or is there anything else I can check?  Also, FYI, iTunes stopped connecting too after I had started downloading small podcasts individually to check the connection after making various changes to the firewall (but restoring the firewall back where it was didn't get iTunes back).  Thanks very much.
-Jim