Why does my 2009 Scion XD slip into neutral while trying to accelerate?

What is your question?

The car has an automatic transmission. It slips into neutral more so in hot weather, going uphill, and after it has been driven for awhile. It happens whether it's in cruise control, or I try to go into passing gear by stepping on it, or manually shifting from D to 3. It has 96,000 miles on it and the tranny fluid was flushed at 60,000 miles. Any suggestions? My warranty runs out in 4000 miles