Did you try hitting the reset button every time you finish a download? It works just fine for me after I do that. You would have to see the
download complete message though that comes right before the write failed messages.
Unfortunately, I haven't had any luck getting any responses on why the message is appearing though. I'm actually quite disappointed by the level of support, or lack thereof, that I have been receiving for the redbearlab boards, I kind of regret buying a redbearlab board due to that reason.