This probably won't resolve tonymatis's situation, but I have run into a somewhat different scenario: at T-39 or T-37 the setup would stop doing things and just hang in there, occasionally swapping the billboard messages and nothing else. As the actual setup is done by a detached process, it means this process is dying for whatever reason. As it turns out, the most frequent reason is running out of memory. It appears that unattended setup takes a lot more memory than regular one. I have just tested my new unattended setup disk in a 128MB virtual machine, and it died at T-37. Increased memory to 256MB, and bingo - it went OK.
