Well, your ISP would say that, wouldn't they? Does your ISP impose a limit on the amount of data you are allowed to download per month? Are you connecting with WiFi or Ethernet? Have you reset your router, and your cable modem if you have one?
You might take a look at your system logs with the Console app (in your Applications/Utilities folder, or from the Launchpad Utilities folder), if you are willing to search through tons of information.
On your Mac you might try some of the Internet connectivity tools at dslreports.com.
Are you experiencing any Internet connectivity or download issues on any of your other devices? You might try this on your iPad or iPhone.
Good luck. Diagnosing network connectivity problems is seldom easy.
Thanks for the input...indeed helpful but still have the issue. To answer your spot-on questions:
ISP limits - none that I know of. And my issue is happening at the beginning of my billing cycle when I would presumably not bump up against any limits.
WiFi/Ethernet - tried both...same problem on both
Router reset - yes, lots of times. No cable modem, using AT&T Uverse with DSL modem/router in one box.
System logs - you were not kidding when you said "tons of information"! Still sifting through.
Other devices - all other devices experience no difficulties. This includes three Windows7 PC's, two iPad2, one iPad, one iPhone4, one iPhone 4S, and the misbehaving MacBookPro.
And the last factor is that this is of course intermittent and only affects some, (but unfortunately many), download sites.
Thanks again for the rapid response!
Download speed test on Mac (WiFi): 8.63Mbps, consistently between 7.5 - 9.0 in 20 tests
Download speed test on W7 PC (WiFi): 4.75Mbps, consistently between 4.25 - 5.25 in 20 tests
Both above tests used the same closest but not fastest server on SpeedTest.net.
Yes, have tried downloading same file from same web site on both machines, both simultaneously and sequentially. Same result: PC download is fine, Mac isn't (and I shudder to write those words).
Well, it would definitely seem to be something on the Mac then All I can suggest at this point is to monitor the Console logs while you are attempting the download to see what errors appear. Hopefully there will be something there that will provide a clue. I guess another thing you could try, since your system is portable, is to see how it behaves on a different network.