I made the mistake yesterday of attempting to do a firmware upgrade on my AVR Dragon from my Windows XP virtual machine running on VMWare Fusion. VMWare Fusion hadn't given me any trouble with USB devices up to that point (quite the contrary), so I didn't think anything of it.

Boy was I wrong. Bad idea. For whatever reason, it does not work. I keep getting the same error after about 11 seconds:

Firmware upgrade failed while preparing write.

I'm going to try using a real Windows machine from work today and see if I can get this thing working again. In the mean time I'm reduced to using my USBtinyISP. Unfortunately it doesn't do JTAG programming, so I can't update my RZUSBsticks until I get my dragon working again.

—sigh—

Update: Found a Windows machine here at work and updated the device with no problems. Back in business. I think the dragon update program was expecting the device to appear back on the USB bus rather quickly after a reset, but with the VM in place it takes a about 100-200ms. I think this was confusing the firmware update program, making it think that something had gone horribly wrong.