Sorry for intruding in your post.
I've got a similar problem when trying to download the Romanian-English Wiktionary. Thought of just asking here for help.
Also, every time I click to download is asks to turn on Wi-Fi even though it's connected.
After that it shows a prompt with the message
"Dictionary file size is %1 (nil bytes)..."
I hit Download an the I get the "Could not save file to:... " message.
My reader it's a Pocketbook Era with firmware 6.8
Thanks,