There are some problems with the windows driver from time to time.

It might be an option to flash from a Linux-Live-CD or an installed Linux system. I would suggest some Debian- or Ubuntu-Live-CD. Here is the wiki about flashing http://wiki.maemo.org/Updating_the_tablet_firmware

Nevertheless, i would try first to just flash the kernel from the fiasco image, according to this: http://wiki.maemo.org/Updating_the_t...rt_topic.21.29