+1 to
@overmind , Cheap machine built wheels will do this, as well as wheels that are not built to withstand the use you are putting them through. It's likely to happen again. The good news is, you now have a set of rims/hubs which are not worth much. Rather than send them to landfill, why not have a bash at the above suggestion? Even if you get a pair of decent rims, you can still have a go at truing or rebuilding your current wheelset with new spokes and keeping them as a backup. If they have buckled twice in such a short space of time, it was likely a bad initial build. Uneven spoke tension being the likely culprit. If that is the case, it won't be long until the spokes fatigue and start snapping on you, even if you get them trued at the LBS every time this happens. The cost of getting a mechanic to true and replace spokes regularly adds up fast.
I find wheel building fun, but it's also a great skill to be able to true a buckled wheel or compensate for a broken spoke at the roadside, if you ride in a group, you'll eventually become a hero in someone's eyes.
If I were you and didn't know where to start, I would begin with getting hold of a spoke key and truing it yourself, then get a book on wheel building and learn the theory behind the wheel build. If it intrigues you, have a go at rebuilding your current wheelset*. Also, no need for expensive wheel truing stands. You can do it in the frame, by securing a pencil to the seat stays with a rubber band and using that to gauge the radial and lateral true of the wheel. I have done all my wheel builds/servicing this way. Dish can also be gauged using this method by flipping the wheel in the frame. You will only need a decent work stand that can hold the wheels up high enough so that you are not hunched over the bike.
*Disclaimer, the other possibility is you are riding a wheelset with too few spokes, and rims not designed to carry your weight, plus bike and cargo, or handle the kind of riding you do. In which case, it's probably a good idea to invest in a stronger set of rims with higher spoke count, rendering your current wheelset useless to you. Fix up and sell on in this case.