engine stall whilst driving?

Hi, I drive a 2003 1.4 petrol megane dynamique. It's a pretty good car for it's age, and hasn't had many problems at all. I've had the car for less than a year, and it's got it's weird starting thing, that on cold starts I have to rev it slightly for about 20 seconds until it's warmed up enough, otherwise it will cut out. I've established is a common fault, I'm not too worried about this problem though... I was driving last night and was going at about 40mph, just about to drop down into 4th as I was approaching another speed limit change. It was like my engine stalled, the dash told me to select neutral and to remove my key card. So I pulled over and just restarted it, and it drove normally. My rev's where at about 2500, so not low enough to actually stall it. I'm honestly stumped, I've been driving it round today, and it hasn't done it. Has this happened to anyone else? Do you think it could be related to my weird start problem?
I'm not really looking to change my car just yet, so I'm quite hopeful this a one off thing. Knowing my luck though it won't be!:d
If anyone has any clue, your input would be greatly appreciated! :)

engine stall whilst driving?