Update, based on your comment: You should use an attribute-starts-with selector, like this:
$("select[name^='blah[']")
This will select any <select name="blah[.........">
which should be specific enough for your needs.
Also, be sure you're running your selector inside a document.ready
context like this:
$(function() {
$("select[name='blah']").doSomething();
});
Without doing this, or after the element in question in the page, the element won't be there to select...so your selector may be just fine, but what it's looking for isn't in the DOM yet. Putting your code in a document.ready
handler like I have above ensures the DOM has all the elements ready to select.