That's a tricky one.
It could be that you are getting interference from somewhere, I used to live in an apartment building and my Wii connection would drop every 20 minutes, as soon as I moved there was no problems at all. I believe it was because of my neighbour's digital phone operating on the same frequency.
You can try changing the MTU value on your router. A setting of 15 seems to work the best. Look at your router's instructions to see how to change the setting.
Other than that you could try buying some sort of signal booster for your router, or perhaps upgrade to a better router. You could also try a wireless bridge and a Wii network adapter (wired); this works by relaying the wireless signal and letting you then use cables to connect. It could get expensive but if you don't have the option of running cables directly then it's an alternative.
Is your Wii and Laptop in the same room? Or is the Wii farther away than the Laptop?