I also have this problem - I have accidentally added an extra block in my email, and I don't even have a bin-symbol appear to allow me to delete it - I had the same problem with templates. Once I added a block there was no way to remove it, and it just sits there creating an empty space in my email. I have just downloaded the latest version of acymailing.
Edit - I take that back. I was using Firefox. I just switched to Chrome and a delete option appears there which doesn't display in Firefox.