"A bicycle wheel is a very strong thing, but only if all the elements are perfect" Paraphrase of Greg Lemond-

I would have to agree with your LBS on the wheel. I have seen this before. Low/lower quality wheelset and broken spokes.........pop/fix/pop/fix/pop/fix, 200 bucks later, same wheel.

This isn't some isolated incident, others have gone through the same thing. I do hear you about not wanting to fork out the dough, but cycling is like that. Replacing a $300 cassette (due to wear) is no fun at all, but sometimes you have to bite the bullet.

Basically, I can say with almost certainty that your wheel will continue to "bust" spokes. This is my opinion of course.