Interesting (?) followup on this:
Today, I got two more eBay Arduino clones, a Nano and a Uno R3. [Pictures of the exact versions that arrived -- US$1.99 and US$3.02 BIN (shipped), respectively, delivered in eight days]
I start out and discover that I'm having exactly the same problem with both of these that I had with the Mini.
I spent about two hours in the splitting-headache-screaming-and-throwing-things stage of frustration after doing CH304G driver rollbacks, searches, etc., etc. before realizing that the "Blink" sketch had uploaded -- this despite nothing in the www.arduino.cc/en/Guide/Windows.htm installation tutorial (now mercifully pulled, apparently) having occurred as indicated as "required." NOTHING in that tutorial reflects how Windows7 SP1 actually deals with installing an Arduino device. I haven't the faintest idea what OS this jackass was actually describing, but it didn't include Win7 as claimed.
Angry? You bet.
So, after this experiment the Nano and Uno R3 apparently work perfectly.
The Mini may actually be bootloaded and working as well. I suspect that two things need to be determined on that, namely the correct method of fiddling the Mini RESET/Download business (for which I have seen three different, imprecise and contradictory explanations) and the orientation of the PL2303HX's RX/TX leads relative to the Mini's. I think that by blind accident during this tsuris, I may have once successfully downloaded "Blink" to the Mini without fully realizing it.
So, if anyone knows the correct way to get the RESET/Download thing synched, I'd be grateful for the information. Other threads I've seen claim people try dozens and dozens of times before they get it right and it's still tricky.
The other thing I'd like to know is if there's a sketch that will do a diagnostic/test/ID/burnin process for new Arduino devices. Seems like there should be lots of them.
Many thanks for any help!