Problem with wireless after waking up from sleep (self assigned IP)

So I have the new Penryn MBP, and wireless works perfectly on it. The only real issue I've been having is if the MBP goes to sleep and wakes up, the wireless will stop working. In the Network Preferences it will tell me that it has a self-assigned IP (169.x.x.x).

Now this doesn't happen all the time, but it is a pain in the ass when it does because I need to reset the router in order to "fix" it. I've tried turning off/on the airport, but that doesn't fix it.

I've read about some of the MBP sleep problems here, but nothing really related to this. I for one, think the sleep function of the mbp works pretty well besides this very annoying bug.

Anyone know if this is a known issue? or even better, if there's a way to prevent this (besides not using wireless/sleep )

 

anyone know?