Rather than start a new thread I hope its OK to post my issue here...
I have exactly the same problem but I'm on Vista 64....
I followed this guide http://nxtemplar.blogspot.com/2009/09/connecting-to-nxt-on-windows-7-64-bit.html
and got the correct 64 bit driver installed, as well as the Mindstorms 1.0 software for XP installed on Vista 64. I also installed leJOS_NXJ_0.8.5. The driver works correctly, I was able to install the NXT Firmware via the Mindstorms software. Then I installed the leJOS NXJ firmware succesfully. I compiled the Tune.java sample, and then tried to nxj it. It links OK, but then I get
leJOS NXJ>Failed to load USB comms driver: Cannot load USB driver
( it then looks for bluetooth which isn't yet available on this PC)
leJOS NXJ>Failed to find any NXTs
leJOS NXJ>Failed to connect to any NXT
an error occurred: No NXT found - is it switched on and plugged in (for USB)?
I trid on a 32 bit XP laptop and it was fine, no problems.
Has anyone had any success getting files to the brick from a Vista 64 machine?