Occasionally Get No Internet Access After Power Up Or Resume From Sleep

I have Win7 on my desktop PC, and sometimes when I start up the computer, it won't have any internet access. On more rare occasions, it will do the same thing when I resume from Sleep. Windows usually solves the problem by itself, but it that takes about a minute or so.

I know it's not the modem or the router, becuz other computers on my wi-fi network can access the internet even when the main PC can't. I did a search and found a few things about reinstalling Office 2010 or disabling IPv6, but that doesn't work for some people. Those posts are also 3-4yrs old, so it seems like there should have been patches