I had the same problem and I was always back to square zero each time I restarted my laptop. Here is how I fixed it windows 8 and should work for windows 7 as well.
1. Right click the wireless sign at the task bar, then select "Network and Sharing Center."
2. Select "Set up a new connection or network" below Change your networking settings.
3. Chose a connection option, choose "Manually connect to a wireless network, connect to a hidden network or create a new wireless profile" and click next.
4. Net work name: The same network name that you have.
Security type: Choose WPA2-personal
Encryption type: Choose AES
Security key: Enter the same password that you always use.
Tick the box "Start this connection automatically."
5. Click next
6. Go back to connect wireless pane, select your network name and enter the same password.
I hope this has solved your problem too because I no longer experience any problem ever since I set up mine.