I'm trying to install some software using aptitude, when I hit the '+' to add a package, I get the prompt "Enter the new package tree limit" - but I have no idea what that means or what to enter. What is a package tree limit?

I'm trying to intall odbc drivers, btw... if that matters.

I've never seen it. Are you just using the Ubuntu repositories or deb repositories too? You might try some arbitrary number like 10 just to see what it will do.

/etc/apt/sources.list:

deb cdrom:[Ubuntu 5.04 _Hoary Hedgehog_ - Release i386 (20050407)]/ hoary main restricted

deb http://us.archive.ubuntu.com/ubuntu hoary main restricted
deb-src http://us.archive.ubuntu.com/ubuntu hoary main restricted

deb http://us.archive.ubuntu.com/ubuntu hoary-updates main restricted
deb-src http://us.archive.ubuntu.com/ubuntu hoary-updates main restricted

deb http://us.archive.ubuntu.com/ubuntu hoary universe
deb-src http://us.archive.ubuntu.com/ubuntu hoary universe

deb http://security.ubuntu.com/ubuntu hoary-security main restricted
deb-src http://security.ubuntu.com/ubuntu hoary-security main restricted

deb http://security.ubuntu.com/ubuntu hoary-security universe
deb-src http://security.ubuntu.com/ubuntu hoary-security universe

deb http://src.braincells.com/debian sid/
deb-src http://src.braincells.com/debian sid/

-------------

all but the last pair are ubuntu...

I tried entering "1", but all it seemed to do was reduce the number of packages displayed through apt & I was still not able to install the package I wanted.

edit: I tried removing the last pair just to make sure, but I get the same result.

Did you see the repository patch on ubuntuguide,org? That might help you out. http://ubuntuguide.org/#extrarepositories

https://imgur.com/ltlv1YL

https://imgur.com/X0BizW3

Try that