I have just had the same problem and tracked it down to the entry in MyConfig.h for the channel which was set to 95, I changed it to 90 and its now working fine.
In my reply above I said I had cracked the problem and all was working fine, this was true for the sensor but I am still getting the same error message on the console "MySensors Version mismatch".
I have tested with all combinations of arduino 1.5.8 and 1.6.8 and MySernsor 1.4, 1.4.1, 1.4.2
Finnaly aparently I solved the problem reinstalling de EasyIotServerV0.9.iso for raspberry pi, but It was still not working right.
I think that my problem was that I was running an arduino with 5V and Its necesary to use a voltage regulator to connect the nrf24
www.mysensors.org/build/connect_radio
Hi Neofox
At the moment I am using an unmodified 3.3v mini pro, I am running the nrf24 at 3.3v . I will try reloading the server image to see if that makes a difference.
I have started to modify a mini for 1.8v working, have done the hardware mods, just trying to program the fuses which is not working at the moment. I am using a uno as the programmer which works fine I can program a sketch to the mini using the ide. When I try to program the fuses using avrdude I get an error saying
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 10 of 10: not in sync: resp=0x03