Frequent " Server not responding " error

At least once a week, my iPad will stop connecting to the internet. I will get a " server not responding error " message. I have an Airport utility router that is about six months old. I have a relatively new router from my ISP. The router is connected to an ASUS desktop about 18 months old.

Sometimes, switching from auto to manual on the iPad gets it working. Sometimes, unplugging the router and desktop restores it. Sometimes, it just starts to work after hours or days for no apparent reason.

I took the iPad to Best Buy. They said the newer iPads have these problems and there is nothing they can do. Am I stuck with a lemon ?