Same here and it seems to be happening with more frequency lately. Here is exactly what is going on with my iPad 2, my and my wife's iPhone 4s and my Mac mini (a friend of mine is also having this problem with his iPhone and ipad with his own wi-fi):
When connected to wi-fi/Internet via my Netgear DGND3300 v2 (with the latest updates as of 5/2/12) and I click on a link/do a search in Safari, the eBay app or even iTunes, intermittantly (quite often) I will get the message "Safari cannot open the page because it is not connected to the internet" or it can't find the server. There are no specific web sites or times of day that this happens.
I NEVER lose the connection to wi-fi. This happens whether I'm 50 feet from the router or right next to the router. This exact same issue happens with both the iPhone 4s and iPad 2. The Mac mini I'm not sure about because I don't use it as much but it did lose Internet connection (NOT wi-fi connection) many times when I was trying to download some updates a little while back.
Here's the strange thing; when im having this problem, I can immediately go to my Speed Test app and run the test which shows it is connected to the Internet. Even stranger, I can almost always go right back to the app I was having the issue with and it suddenly, magically works again but the same problem always returns a few minutes later.
Now before you blame my router, I have a Windows laptop that I use quite a bit that is connected wirelessly to the exact same router and I never have these problems.
All of my devices are up to date and I've tried resetting EVERYTHING. I have gone through ALL of Apple's online troubleshooting and scoured the Internet and haven't found a single real fix for this.
Would someone at Apple care to address this?
PS Guess what? I tried to submit this reply and got this error message: "An error occurred while trying to submit your post. Please try again." No doubt this was caused by the same issue.