I was having the exact same problem and a post by another member fixed it ... here are the steps that fixed my situation:
Make these settings on the router:
Under Advanced --> QOS engine --> QOS engine setup:
Uncheck Dynamic Fragmentation
Under Advanced --> Advanced Wireless -->Advanced Wireless Settings:
Uncheck Short GI
Under Advanced --> Wi-Fi Protected Setup:
Uncheck enable
Under Advanced --> Secure Spot:
Uncheck Enable Securespot services
Under Setup --> Internet --> Manual Internet Connection Setup:
Uncheck Enable Advanced DNS Service
Under Setup --> Network Settings --> Router Settings:
Uncheck Enable DNS Relay
Under Setup --> Network Settings --> DHCP Server Settings:
Check Always Broadcast
Under Setup --> Wireless Settings --> Manual Wireless Network Setup:
Set 802.11 Mode to Mixed n,g,b
Check Enable Auto Channel Scan
Set Transmission rate to Best (automatic)
Set channel width to Auto 20/40
security mode to WPA personal
Set Visibility Status to visible
Under Wireless Security Mode set:
Set Security mode WPA-Personal
Set WPA Mode to WPA2 Only
Cipher type AES
Pre-Shared Key is required
After making the changes above, reboot the computer(s) on the network or run ipconfig /renew.