I have the same problem.

I have this message (Suitable USB device not found, waiting) if i run flasher on Seven 64, Xp Mode or directly from my n900.

On windows I tried
flasher-3.5 -k kernel -f -R
flasher-3.5.exe -k kernel -f -R

And on n900
flasher -k kernel -f -R

Always the same message ^^

EDIT : Finally, work fine in XP mode. the driver was corrupted.

Thx for all ^^