:( Since I updated to 1.6.4 ide ALL my arduino boards have been giving me hard time while uploading. Sometimes the sketches upload and sometimes they don't. I' m using PC windows 7 64 system. I am aware of the FTDI issue. I have updated my win 7 but there was no problem untill i updated the arduino ide. Even while the problem happens I open the device manager and there are no problems with any of my arduino boards getting recognized. This is driving me crazy. The only work arround I managed to do so far is that after successfully uploading any sketch I have to open the serial monitor and KEP IT OPEN !! so that when I try uploadding a newer sketch to accepts it. Please help.
I've never used that IDE version. Can you try the latest and greatest 1.6.5 R2? I've been using that for a couple of months with various arduino boards and my own boards with genuine FTDI chips. No problem. Before that, I was on 1.6.0 for a few months and 1.0.6 and 1.0.5 for a couple of years. No such issue.
Oh, try another computer also.