Windows 7 - Random loss of connectivity on working wireless network

hi

i have a good wirelss N network at home, no major issues, and i have noticed that randomly my netbook with win 7 ultimate will not find the wireless network anymore, it's really random, like works great until the night, then when i start the pc in the morning it will not find the wirelss network anymore, although it can find other networks.

and i noticed that with my other wireless network, in italy, happens the same, every XX time, the pc will not find the wireless it was connected to anymore.

on a side note, if i restart the wireless modem, it will work fine again, however this is not a solution, and it shouldn't work like that. i have an android phone which was connected in the time my pc wouldn't find the network and another xp machine perfectly up and running.

for some weird reason when this happens on battery, removing the battery and leaving the pc without for 2-3 minutes seems to fix the misterious problem, however i was on AC power, i restarted the pc like 5 times and nothing, then i went extreme and i removed the power cable while he was working (bad solution of course) shocking it... and guess what?? it found the wireless and it's now connected. one other time, it found the wireless network, i put the password, then it "did" something and then the wireless network disappeared like a ghost from the network list, what if i typed a wrong password? where is it gone??

can somebody explain the mistery? the network is discoverable and "broadcast network ID is of course always on".

is it a windows 7 bug? wireless drivers? i have an atheros wireless card AR 928X on Asus N10J netbook.

thanks
gabrio