Jon, have you done any electrical work to the VX recently? A little while ago I tried to do Raque Thomas' mod so that when I hit the stock key fob lock release a second time it actually triggers the rear door popper. It didn't quite work, but I realized that I had installed a relay incorrectly and it was constantly drawing power even when the VX was off, thus running the battery down a little bit. It was doing everything that you are describing; taking longer to start than normal, but running fine afterwards. After I realized what was going on and rewired the relay the problem went away.
Maybe you have a short somewhere that is draining the battery.
"The major difference between a thing that might go wrong and a thing that cannot possibly go wrong is that when a thing that cannot possibly go wrong goes wrong, it usually turns out to be impossible to get at or repair."
-Douglas Adams, Mostly Harmless