after successfully programing and using my atttiny85 for about a week, all of a sudden it wouldn't work any more. i got the stk500 ... error.
so i arduino searched and tried all of the suggestions (unwiring, rebooting,rewiring,updated driver, verifying board, verifying port, checking the capacitor, you name it), nothing worked.
same with the adafruit search, and google search. forums, everything. the UNO board still worked fine (it took and ran programs) but i could not get it to program my tiny anymore.
so i started all over, and re-read the M.I.T. high-low tech instruction page. i followed the instructions, and it started working again.
I am convinced that reloading FILE-EXAMPLE-arduinoISP to the UNO board straightened things out.
i hope this helps somebody.