I'm having issues with a 100nF capacitor between FT232R DTR and Atmega328p reset line having too much capacitance between toggling the power on/off.
It causes the pc driver not to detect the FT232R (Unknown device).
If I press the reset button while the board is powered down or wait enough time, the capacitor will be discharged and it works then fine.
Schema between the DTR and Atmega reset Line: ATMEGA-RST 100nF | 10kOhm DTR -----||------+------^v^v^----- VCC | +--RESET-SWT--GND
Could the problem be that the capacitor is not really 100nf but bigger thus taking more time to discharge after powering down the board?