I was having the same issue with the work laptop not staying connected via the home wireless. A complete power-down of laptop, router, and cable modem, followed by a sequential power-up--modem, router, laptop--worked for a while. Ultimately, the router needed to be reset--it's possible that the issue with my work laptop was the first hint.

At first, we thought it was an issue with the laptop, which was a particular model that other folks at the day job had the same issue with. It's apparently touchy.