2000 Chevy Venture w/Intermittent Starting Problem

This is my second post regarding this topic. I am just praying someone could have another suggestion. I have a 2000 Chevrolet Venture LT that will not start sometimes. When I go to start the van I turn the key on were the lights come on the dash board but as I finish turing the key the rest of the way it is absolutely dead, no crank or nothing just dead. I have replaced the starter, the ignition switch, the neutral safety switch, the passkey module, checked the battery connections and even the relay box on top of the battery and I think that is about it. All totaling about $700.00 and its still doing it. I took the ignition key off my key ring because someone suggested that maybe there was something interferring with the frequency of the passkey and for the past week it did not act up, until today when I put the key back on the keyring. I took the key back off the key ring and it didn't make a difference. I sat and messed with it for about 5 minutes and opened and closed the power door and then it started. Does anyone have any other suggestions or help. We are planning a trip in 27 days and really don't want to take a vehicle that starts when it feels like it.

i know someone that their battery cable kept poping off and the car wouldnt start.

They took it to the dealer, and never found out whast it was, but the bettery cable was worn down, and it was poping off.