ok, I think I'm getting closer. I updated drivers, rebooted phone and pc, and tried your file again. This time, I got:
Pushing the update zip file to your sd card
Do not wipe data or cache...
Pushing 5.5.893...
daemon not running. starting it now on port 5037
daemon started successfully
failed to copy 'update893.zip to '/sdcard-ext/update893.zip': Permission denied
Pushing 5.9.901...
failed to copy (same as above except 901)
rebooting phone to bootloader..
Told me to disconnect and I did. I think if I fix the permissions it might work, but I don't know how to do that.