Aha, I fixed it for me at least. It was some permissions/authorization issue between gmail (what I was using as my send-from address) and quickbooks.
What I did:
1) Create an invoice and fill out whatever is necessary (you won't actually be sending it)
2) Click "review and send"
3) On the review page, click the pulldown menu for "from" and select "remove gmail address"
4) Now click the pulldown meny for "from" and select "add gmail address" to re-add your gmail
5) follow the steps that come up to authorize you gmail account
I hope that helps others
