The same problem occured when I first got my truck and I did the new battery & starter thing. It worked then it happened again. But now the post connections were smoking and hot. Found out that the engine froze with cylinder #6 not firing. Turned out to be a head problem (water leaking into the cylinder) causing the engine freeze. Replaced heads and she's running like a champ.
The problem happened again but now without the smoke and heat from the terminals. Figured it was due to loose side terminals. Somehow the side terminals were bad and could not be tightened (probably from all the heat from the first time). So I changed it to top post and it starts fine now.
Hope this helps.