I can't upload program using my ftdi cable! Could it be the I2C connections that block it?
here is a part of my pcb (the reset capacitor is no more there)
Since you have a separate ICSP and FTDI header, if I were you I would just cut the trace that leads to the reset pin on the FTDI header and add the capacitor in. That way you can use both methods without constantly having to modify the board.