Hi Kaylamarie12,
I had exactly the same issue with windows 7 not connecting wirelessly to my NAS, however there were no issues with a wired connection.
This is the only solution that worked for me (I think it has been suggested by Piptech earlier).
First start an administrator console by entering cmd into the searchbox on the start menu and then do ctrl+shift+enter instead of just enter. In the console enter the following commands to change the MTU:
netsh interface ipv4 show interfaces
Take note of the id number of the wireless interface.
netsh interface ipv4 set subinterface id mtu=1460 store=persistent