Whydoesmy car stall on the highway when at speed I shift from gear into neutral?

What is your question?

Whenever I am driving at highway speeds and I shift into neutral (e.g. when I need to slow down), the rpms suddenly drop from around 2500-3000 to almost zero. Sometimes the engine recovers and doesn't stall, other times the engine quits cold turkey. This has happened to me more than a handful of times. I've learned to deal with it, but I'd like to know what the problem is. It doesn't matter if the weather is hot or cold. I thought it might be the Idle Air Control Valve, but now I'm not too sure.