MacBook Pro Retina slow wakeup on battery

My half year old Retina MacBook has developed a bad habit since a month ago.

While running on battery and with WiFi active i experience the following:

When waking from a deep sleep (when the network connection has been turned off) I am presented with a logon screen with no curser and with a blank login-window - the "password" text is missing. In about 5 to 8 seconds the curser and the text in the login window appears, and i can login.

After logging in, the WiFi-connection feels unstable and slow, and the doc in the bottom of my screen is slow to show up, and does so like in small increments.

And the whole machine feels slower than normal.

When looking at the system log I can see several pages of unsuccessful network-upstart procedures and faults. But not being a unix-wizzard, this doesn’t help me much.

When started up connected to power this does not happen, neither it does when WiFi is off and the Mac is connected to the internet by Ethernet cable.

I have done the following:

- tried it on several different networks and routers, different peoples and companies' networks

- installed a Time Capsule AirPort Router

But the problem is still the same.

I have also done:

- Restored Mountain Lion 10.8.2

- completely reset the Mac - reformatted the disc an made a completely new install of Mountain Lion 10.8.2 and tried it with only Apples own apps coming with OSX Mountain Lion 10.8.2

None of this helped. Whatever I do, I end up with the same problem.

Have any of you an idea of what can be wrong??