I've been working on the same problem. I found out that the drivers that
come with ubuntu are $#!+. There is supposed to be a work around.

First I Googled 5570z wifi (I have an Aspire 5570z which also has an
ar5007eg)

I got some links to some download if madwifi. The first ones that I
downloaded were outdated. The second ones I downloaded were supposed to be
good, although all I got were errors when I tried to install them.

http://madwifi.org/

http://madwifi.org/wiki/UserDocs/FirstTimeHowTo

That is where I am now. No luck so far.