Please see the following tasks for you to do:
If you have not done this yet, please remove all wireless profiles stored in your computer. Easy Way to Delete Wireless Network Profile in Windows 7
Re add your SSID (wireless network) that you're trying to connect to with the correct encryption.
If none of the above suggestions worked please install and run Xirrus Wi-Fi Inspector
from one of your wireless computers. Double click the Xirrus Icon on your Desktop, Tap the Printscreen key on your keyboard, open up Paint then choose Edit from the Menu and select Paste, then SAVE it. Upload and attached the file here.
Post your speedtest result: Speedtest.net - The Global Broadband Speed Test