For the FirewireGUID problem, there's a thread
here (registration required) that outlines how to get around it (although the developer should have a fixed version on installer by tomorrow).
To fix it, I did the following from an ssh shell(run as root):
chown mobile:mobile /Applications/iSlsk.app
chown mobile:mobile /Applications/iSlsk.app/*
And then I also used this ioreg binary that the developer included which generates a firewireguid. I've attached it to this reply, for those of you who don't feel like registering on the above site. Simply run it as user mobile (make sure you run it as user mobile, if you are using firmware 1.1.3 or greater - this tripped me up at first, as I ran it as user root but iSlsk still couldn't find the firewire guid when run from my iphone, yet run from the command line, as root, it worked, although it didnt find any of the files I had downloaded.)
Hope this helps.
edit:Also, if you are using 1.1.3 or greater, the files are actually in /var/mobile/Media/Downloads.