I love it when people blame real estate agents for the mortgage crisis...especially first-time buyers. When your agent asked you to check in with a lender, she wasn't automatically asking you to spend more than you can afford. That mistake falls squarely on the shoulders of the buyer - sorry, but it's true.
I've found that many buyers don't, in fact, know what they can afford. And in my northeast region, no offer will be considered without the backup letter from a financial institution that has done at least some preliminary investigation that you are able to get a mortgage. The "pre-qualification" letter you referred to was, indeed, not enough of a recommendation, because it didn't include even a credit check on the buyer. A pre-approval letter is a more thorough investigation of your ability to buy a home. Not having this done results in wasted time (for both buyer and seller); even in this market, a good, well-priced property can and will get multiple offers. Isn't it better to be ready to have all the required paperwork at the ready?
But why listen to what I have to say? - I've only been selling real estate for over 18 years...
Pat