I've read lots of threads concerning "odd" behavior of arduino boards on Win7x64, but I haven't found any reliable solution.
I have Arduino Duemilanova, win7x64, Intel i7 CPU,oficcial Arduino IDE, no touch into bootloader or hardware of the board at all, basicly I am playing with just naked Duemilanove.
But after about 2 uploads of sketches (not exactly 2, but give or take), IDE writes that error "avrdude: stk500_getsync(): not in sync: resp=0x00", after reopen of IDE and repluging the Arduino, my f*/-ing windows goes crazy and popups windows like "USB device not recognized", "Drivers weren't installed properly",in Device manager "Code 10. unable to start device" or "Unknown Device" with yellow exclamation mark.
0] reatarting the computer
1] uninstalling arduino from system & repluging
2] reinstalling drivers for the newest FTDI drivers
3] uninstalling ALL com devices
4] changing setting of Arduino COM port
5] wait for few hours to chill out
6] second computer (almost the same configuration, onlu CPU is AMD 6core 64bit)
and I did combined all those action randomly in past few days being more and more desperate. It gives me few chances to upload the sketch sometimes and then it happen again.
If you have any suggestion, I'd be glad if write it there..it really spoils my joy of this new toy