Using nrf24l01 with mpu 6050 unstable
I could not figure out what was wrong, but I changed to this library for NRF24: http://tmrh20.github.io/RF24/

and I started using the GY-85 with the FreeIMU Library : http://www.varesano.net/projects/hardware/FreeIMU

Following this advice:
http://forum.arduino.cc/index.php?topic=164222.msg1539961#msg1539961

It works now, so if it was SRAM as @Avamander suggested, it was not on my side.