I've jus recently been experiencing trouble connecting to Wi Fiwith both my Acer A100 and my Galaxy S2. My netbook was showing EXCELLENT signal strength and locked on immediately. But the Tablet and Phone kept saying POOR signal or NETWORK DISCONNECTED.
Double checked my password. Disconnected, "FORGET" network, changed the band frequency connection from Auto to 2.4.GHz and that worked for the phone, but not the tablet.
In the end I turned off both devices as well as the router. Turned router back on and then each device. Input passcode and voila! Connected! Hope it doesn't happen often.