avrdude: stk500v2_getsync(): can't communicate with device: resp=0x01

Incredibly frustrating problem which has been plaguing me for some time.

Windows 7 64 Arduino mega 2560 r3 latest software environment.

So, I've been using the mega for quite some time, and periodically, I get this error. I've tried absolutely everything. (well, I can't have done, but you know what I mean!!!)

reinstalled drivers for the board, no change tried the older drivers in the zip file, no change removed all sofware, rebooted and reinstalled, no change replaced the usb cable, no change

Installed the same drivers with the same methods on my wife's laptop, same cable, same mega, works perfectly, so its clearly my installation somehow. I'm at my wits end with this thing. It was working this morning, nothing has changed. 10 mins later, good old avrdude pops up, and no joy ever since.

I've tried the loopback test, but I only get one response (I was expecting duplicates?)

Anyone got any other ideas?

Thanks in advance

One trick that sometimes makes driver replacement work better is to not uninstall, but delete the device in control panel, reboot, and driver will install from a cleaner slate.

The USB, try different ports, especially back panel ports often work better.

tried that, deleted everything, made sure it was coming up as unrecognised device before installing the right driver, still no use.

Tried all the ports on my machine, same on all of them

Can anyone think of anything I haven't tried yet? or a way of fault finding the communication?