Smartphones connect to wireless, but computers don't?

So, I've been having a problem with my internet the last couple of days. My roommate and I both have smartphones (androids) that connect to our wireless internet just fine. However, both of our Dell 1525 laptops (I have Vista, she has Windows 7 and ubuntu) and another HP pavilion G-series laptop running Windows 7 have been having issues where the internet drops out. On my computer, I will sometimes get full connection and sometimes it will drop out to "Local Only." My roommate can't get any connection on either of her OSes or the HP. We've tried rebooting all laptops, and unplugging the router several times and sometimes it works for me, but it never works for her. I tried changing the encryption type and the channel to no avail. (We use WPA-PSk/WPA2-PSK.)

I intend to call the ISP soon, but does anyone have suggestions for troubleshooting what might be wrong? I don't understand how our smartphones can connect but the computers won't...