Thank you for your reply. I have looked at the links, but I am not sure any of that aplies here. Everything else work fine on the network. All other machines go in an out of sleep/wifi without problems. The routers (in my case) are Apple routers with latest updates. The frequency space is also not very crowded. It is just the iPad 3. It has no problems while on the net. It is just reconnecting after sleep.
The screen brightness up/down had no effect on my iPad 3.
At least from what I could see.
From the net it looks like this issue is not new to the iPad users.
I just tried my girlfriends iPad 3. Same problem. No reconnect after sleep.
Maybe an software update will address this some time...
Update: It does not always happen.
Could have to do with for how long it has been to sleep.
Cheers,
Paul