[TxMt] Occasional "Precondition failed' error in blogging bundle

[Chris]

One super-nifty feature of the blogging bundle is the drag-
and-drop image uploading, which sets you up with the 
appropriate image code in your blog post. Often, however,
I have received the following error instead of a successful
upload:

Received exception:HTTP-Error: 412 Precondition Failed

It seems to happen with some images and not others.
Anyone seen this and have a solution?