I have tried to install v1.1 under multiboot with this my guide:

1. Download and install multiboot 0.2.11 and backupmenu-multiboot 1.1
2. Download latest backupmenu package and copy it to MyDocs
3. Open an xterm and become root user with
   sudo gainroot
4. Remove backupmenu's old files with
   rm /usr/share/backupmenu/*
5. Go to filesystem's root with
   cd /
6. Extract backupmenu's new files with
   dpkg-deb --fsys-tarfile /home/user/MyDocs/backupmenu_1.1-1_all.deb | tar xv ./usr/share/backupmenu/
7. Add execution permissions with
   chmod +x /usr/share/backupmenu/*
   chmod +x /usr/share/backupmenu/.functions.sh.swp

Unfortunately BackupMenu 1.1 doesn't start (the 0.62 was working instead).
The last message I see is "chrooting" then after some seconds N900 shutdown (watchdog ??)