How to format a USB drive to EXT4 - so that it reliably writes more than once from a Readynas 

Get these tools:
to create an ext4 partition
http://download.cnet.com/MiniTool-Partition-Wizard-Home-Edition
(freeware)
to be able to read it on Windows
http://www.paragon-software.com/registration/extfs-windows.html
(requires registration)
Paragon can be loaded just as required (don't integrate unless needed.
No reboot was required to install these two and use them on Win7 Pro :)

(or use http://www.diskinternals.com/linux-reader/
or
http://sourceforge.net/projects/ext2read/files/latest/download
neither of which I have tried)