D&D 4e is complex enough so that there's always going to be a hole that'll allow determined players to break the system. Right now, the clever minds of the Character Optimization board have figured out a way to generate an average of around 130 damage per round at level 16; the same character can reliably do over a thousand points of damage in one round at level 30.
In MMORPGs, there's a basic design tenet: hundreds of thousands of players are going to find exploits that a hundred developers won't see, just because there's more of them. Same thing applies to D&D, alas. Therefore, the only completely impervious fix is the one where you ask your players not to be jerks.
That said, Jadasc's pointer is a good one, although I think his link is wrong: the errata PDFs here contain a lot of fixes. It's kind of a long document, but it's not actually necessary to read the whole thing -- just check the stuff your players take or the powers you take.
Oh, and one final addendum: the Essentials rulebooks, coming out this fall, will contain all the fixes to date. If you're going to be starting the game in a month or so, it might be worth waiting; depends on how much one hates reading errata documents.