LIGHTROOM: Email photos doesn't work with Thunderbird on Windows

When attempting to use the 'Email Photos' option in LR 4.3, I always get an error message. Here's a description of what I'm doing:

Select 2 images in an open folder.
Right-click and select 'Email Photos'. Dialog opens w/ 2 images.
Leave 'To' field blank; Enter Subject; Mozilla Thunderbird selected in 'From'; any preset selected (I've tried several); click send.
LR starts processing the first image.
Thunderbird opens, but does not open a new message window.
LR stops processing after the first image (progress bar stays in the middle)
After a couple minutes, Thunderbird closes and a message box appears, "Can't Launch the default email client".

Clearly, it can launch the email client, but it apparently can't communicate with it correctly. Also tried it with just one image, got the same results. Then, I tried it again with 2 images and adding an email address in the 'To' field. Still got the same result. So, it appears to me that LR is unable to communicate correctly with Thunderbird.

Anyone have any idea if LR works correctly with Thunderbird on Win7 platform?