[pierrelux]

After many hours of tests, I found finaly the follow solution (working with Windows7):

1. Delete ftdi driver (CDMuninstallerGUI.exe) ,
download from : http://www.ftdichip.com/Support/Utilities.htm
explanation : http://www.ftdichip.com/Support/Utilitie...eadme.html
2. Install the new FTDI driver : CDM v2.12.00 WHQL Certified.exe
3. Download MProg3.5 program from http://www.ftdichip.com/Support/Utilities.htm
4. Unzip and run MProg.exe Arduino Nano connected, and see:
https://www.youtube.com/watch?v=RZH_qGautqM

I start Arduino Ide, my Arduino Nano was connected to COM Port 11.
Then start EasyWeather RS232 Logger : OK,
Start Cumulus : OK

I hope this help