Where is it planning to get 27GB of packages?
Try running apt-get -f or removing the package that you forced then update.
Debian Distro Stats on sarge... 15749 packages, 1472 maintainers, 29193 MB installed size, 9115 MB compressed size
Debian Distro Stats on etch... 18684 packages, 1723 maintainers, 41370 MB installed size, 13464 MB compressed size.
Debian Distro Stats on sid... 19816 packages, 1777 maintainers, 45862 MB installed size, 15225 MB compressed size.
My system isn't even 27gb and thats with almost 2k packages installed and with 2 yrs of usage.