I saw that error only when I was not already logged in with the browser, which should not be the case according to your description. The only thing that comes to mind is that your path to the cookies file is a bit strange; in my system, *my* cookie file is under "$HOME/.mozilla/firefox/<strangely-named-directory>/cookies.txt". In your case, I see that you're using Logical Volume Management (which I don't know), so I would suggest to double-check that the path you're using is that of the cookie file actually produced by firefox for your account. Try to

shell$ grep zooomr /LVM/.firefox/cookies.txt
[download]

and see if there are lines coming out. Then try to logout from Zooomr, and see if the cookies changed, try to delete them from inside firefox and re-login, etc.

Last, but not least, which versions of Perl and libwww are you using?