as an IT professional, i can say that driver installation packages for MOST printers are really bad and confusing, but HP is the WORST, hands down, because they're HUGE, take FOREVER to install, and OFTEN don't work, and cannot easily (let alone quickly) be uninstalled. and often, shortly after working for some time they stop working, due to communication problems. and of course these 'drivers' come with giant packages of unnecessary marketing bilge.
i can no longer recommend HP printers, a brand that in the past has been GREAT, starting with early lasers and inkjets.
back to this thread, i too have a 6500 e709n and have experienced all the aggravation shown here. my best bet has been a combo of the 'scrubber' complete uninstall tool, plus deleting everything in %temp% folder, combined with reinstall, and then it sometimes works, including finding the scanning feature. oh and i added firewall rules in and out for ports 9290 and 9500. RIDICULOUS and something no typical consumer will ever figure out, let alone take the time before throwing it in the garbage.