@m26872 Thank you for your suggestions. I have now tried them (and many more) but still can't it to work. It's really not a big problem since I can program them using an Uno as ISP instead but it's really annoying that I can't get it to work.

I have checked my chips, they are all at mega328P-PU and I have tried many of them with the same result. I have soldered many nodes, thinking that I didn't make the solder connect through the holes but without any luck. I have tried different sockets to make the connections better and I have traced the entire node without finding any broken connections.

To get the sketch loaded I use Nick Gammons board_programmer with an Uno and use the LilyPad boot loader which enables the internal 8 MHz (Using pin 9 as clock instead of an external crystal). After that I program the Uno with ArduinoISP, set the programmer to Arduino as ISP and upload the sketch with "Burn with programmer" command.

I have switched USB-cable, USB outlet on the mac, breadboards, dupont cables, capacitors (different ceramic but all show too little capacitance), Atmegas and FTDI programmers. I have tried all combinations with 3.3 and 5 v without any luck. Programming Arduino Pros with the FTDI works fine.

I have tried the Mincore and Gert Sanders OptiBoot. I have tried to manually reset the chip connecting the reset pin to ground briefly when programming. I have tried lowering the baud rate to 9600. I have tried to load the Uno bootloader together with a 16 MHz crystal and 2 x 22pf capacitors and then the FTDI. I have tried larger electrolytic capacitors.

Last week, when mimicking the slim node on a breadboard, I managed to get the FTDI to work a few times but can't really say exactly what I did. Now I can't get it to work anymore.

All in all I have spent many hours trying to figure this out but without any luck. My nodes look just like the ones I see in your pictures.

Could it be that the internal 8 Mhz is too unstable to work?
Capacitors being too small? I've seen some reporting that they succeeded with larger...
Bad connection somewhere > momentary voltage drop?
Cheap FTDIs?
Mac USB-power maxing out?
Bad atmegas?

Please help me solve this annoying problem.