"I've had two Galaxy S II phones now, and I've had the same problem with both devices. The phone's wifi is great -- when it works. Although I noticed that the death grip lowers the wifi signal bar, I can still browse the internet and download apps just fine.
The problem is that, at times, the phone will show wifi connectivity and yet, I can't browse the internet or access the App Store. I'll have to shut off the wifi multiple times and even this doesn't work 100% of the time. Shutting off the phone and turning it back on works 100% of the time.
Since this has happened to two phones, I'm beginning to question whether I have an issue with the wireless router because I have not come across this as a prevalent issue. At the same time, my laptop and a family member's iphone doesn't have the same issue."