Hi Bryan,
Is there a sequence of events that makes the freezing more likely, or is it just happening while it's receiving signal? Next time this happens, can you do the following before you terminate the application?
1. Open Task Manager and right click on freedv.exe in the list.
2. Select the "Create memory dump" option and note the location of the dump once it finishes creating it.
3. Send an email to me off-list with that dump file attached (you may need to zip it up or otherwise upload to a file sharing service if it's too large for email). I can provide this file to a debugger to allow me to see where it may have froze.
Thanks,
-Mooneer K6AQ