I have the same router with the same problem and I devised a solution involving a wired computer sending a reboot command whenever the router does that (it involved telnet, a telnet scripting tool, a batch file and a hotkey program). It's a bit involved and apparently a bit overkill… As noted above by gs44 I guess you can just disable an enable the wireless and it'll be fixed.
One thing that just popped into mind is that by default the red button on the back of the router is rigged to toggle the wireless on and off. Press the red button for a second or so and the wireless will turn off (the light will go off on the front of the router). Press the button again for a second to turn it back on. I'll try this the next time the router decides it's time for the wireless to crap out to test it, but it does essentially the same thing as what gs44 said above.
The benefit of using the button is that you don't have to hook a computer up tot he router if you don't have one already hooked up, you don't need to reboot your router and it takes all of 5 seconds to push the button twice. It also saves you the headache of going through what I did and setting up something to send a reboot command to the router.