"Send Again" Function doesn't work. Apple Mail Mac OS 10.8.4

Hello there! I have an Apple Mail running under Mac OS 10.8.4. I often use the "Send Again" function, I just edit the date and added some notes on it and it works perfectly for my daily reports! However, these past few days it seems so odd. By using the said function I can no longer edit the message. And while I'm trying to close the new Mail window that I have open from the Send Again function it won't let me do so. So I forcibly quit the Mail and re-open it again. And upon re-opening application the mail was on the draft and that message area was blank already. I have to re-type the message again. I tried the Rebuild function but same problem persist. I ready reformatted my Mac and just returned the Mail folder inside the ~/Library to have a fresh preferences file, however same problem occured. I cannot find any solution on the web. 😢 Please help. Thanks in advance!