Hope this helps for those with C4780 or similar. Unfortunately, HP 'partially' sunset the Mac support for previous models. Now the printer is working on my wi-fi network without USB connection. Click on +, the HP printer should also say Bonjour as “Kind”.Click + to add printer…should see a listing for the network printer – click on it. On MacOSX, go to System Preferences > Printers & Scanners.Go back to router setup and put back original SSID and WEP settings.Configure settings exactly as what it was originally before (SSID and WEP password). In printer’s portal site, go to Network tab > Connections > Wireless (802.11) > Wireless Setup.In General Information section, type in printer’s URL on web browser. On printer, you should see the signal bar now.From the details, go to the router settings and rename SSID to the default printer’s SSID (e.g. On printer, Print Network Configuration page.On printer, go to Scan > Wireless Menu > Wireless Settings > Restore Network Settings.(Please note: this was done on MacOSX 10.9)

Before proceeding, make sure to write down your router wireless settings. There seems to be a flaw in the design or software of the printer that forces it to change to some default network and there is no install wizard that works with Mac OS wrote: I has no such luck with the basic info the HP 'experts' provided. Although I had had an initial issue of accessing the printer's portal, I was eventually successful and made the changes. Er 12 hours of searching and reconfiguring I found your post.

Hp c4780 wireless setup utility