Basically, if a hacker can interrupt the encryption key negotiations between the router and client, the key can be sniffed and cracked. Wired's article I've been told a fix has been determined and is being developed for deployment. This will have to go out to all access points. If you have an older router, now would be a good time to update since manufacturers probably won't update older units.
Update: Flaw in widely used Wi-Fi Standard could allow snooping - The Security Ledger Is the flaw serious? Yes. Is it something that's easy to exploit? No.
Not easy at all, you have to interrupt the 3rd of 4 encryption exchanges and capture everything. If someone does this, they want to be in YOUR network. The chances of being struck by lightning are better than being the target of this attack, unless you are dealing with sensitive information.