When I tried to install a Debian server as domU in CentOS (dom0),
I got this error message:
E: Couldn't work out current architecture

Code:
[root@xen debian1]# debootstrap arge /mnt ftp://ftp.uk.debian.org/debian
E: Couldn't work out current architecture
Luckily it's easy to fix this issue:
What we need to do is to add new parameter --arch i386


Now this command is running well in CentOS 5.4..

Code:
[root@xen debian1]# debootstrap --arch i386 lenny /mnt ftp://ftp.uk.debian.org/debian
I: Retrieving Release
I: Retrieving Packages
I: Validating Packages
I: Resolving dependencies of required packages...
I: Resolving dependencies of base packages...
I: Checking component main on ftp://ftp.uk.debian.org/debian...
I: Retrieving adduser
I: Validating adduser
I: Retrieving apt
I: Validating apt
I: Retrieving apt-utils
I: Validating apt-utils
I: Retrieving aptitudem
...