I use Continental Race-Lite tubes......... don't know if they're considered "ultralite" or not but I think they are lighter than the regular tubes. I haven't had any problems with them. Started using them 'cause that's what my LBS carried in a 650 road tire with a longer valve stem. The only flats I've gotten are obvious ones, like a piece of glass stuck through the tire.Occasionally , a shop will get in a bad batch of tubes where there is a weak spot at the valve stem. It doesn't happen often, but it can happen. Ask the shop if they've had many people back with flats from those tubes. And take the tube in and show them where it failed. They might give you a new one free. Or be able to explain why it happened.

Unfortunately, you might just be having a run of bad luck with flats!!!
Look at the bright side....... you'll be a whizz at changing tires and be able to help and impress all your riding buddies.