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I cant take credit for this solution but has so far helped me.
I too was getting the wifi drop and cant connect to network error even when trying to enter my password.
Try going into your router settings through the IP address and use WPA2 for security and change your encryption from TKIP+AES to just AES.
Upon doing this I connected right back to wifi without even being prompted for my password, the wifi signal is stronger throughout my house, and as a side benefit, seems to have increased my 3g signal. It was interfering maybe?
HP Windows Vista