nrf24l01+ works on channel 10 but not channel 82?
What it turned out to be was that I was running it off the internal 8Mhz oscillator... Even though there had been no problems at channel 10, running the higher frequency channel eg 82 could not.

So using either an external 8Mhz or 16Mhz crystal fixed the problem, likely caused by inaccuracies of the internal oscillator.