I got a similar bugreport via mail by Mario 'BitKoenig' Holbe who thanksfully 
debugged this issue. It's related to the case-sensitivity with Debian's 
iocharset=utf-8:

# mount -o loop,ro /home/ftp/pub/Software/Linux/grml/grml.deb.at/
grml64_2009.05.iso /mnt
# mount /media/stick0
# mkdir -p /media/stick0/boot/addons 
# rsync -rlptDH --inplace /mnt/boot/addons/bsd4grml /media/stick0/boot/addons//
# rsync -rlptDH --inplace /mnt/boot/addons/bsd4grml /media/stick0/boot/addons//
# umount /media/stick0
# mount /media/stick0
# rsync -rlptDH --inplace /mnt/boot/addons/bsd4grml /media/stick0/boot/addons//
rsync: open "/media/stick0/boot/addons/bsd4grml/LICENCE.TXT" failed: File 
exists (17)
rsync error: some files/attrs were not transferred (see previous errors) (code 
23) at main.c(1057) [sender=3.0.6]
# ll /media/stick0/boot/addons/bsd4grml | grep -i licen  
-rwxr-xr-x 1 root root   23098 Apr 11 12:36 licence.txt

Without iocharset=utf-8 it works:

# mount -o iocharset=iso8859-1 /media/stick0
# mkdir -p /media/stick0/boot/addons
# rsync -rlptDH --inplace /mnt/boot/addons/bsd4grml /media/stick0/boot/addons//
# rsync -rlptDH --inplace /mnt/boot/addons/bsd4grml /media/stick0/boot/addons//
# rsync -rlptDH --inplace /mnt/boot/addons/bsd4grml /media/stick0/boot/addons//
# ll /media/stick0/boot/addons/bsd4grml | grep -i licen
-rwxr-xr-x 1 root root   23098 Apr 11 12:36 licence.txt
# rsync -rlptDH --inplace /mnt/boot/addons/bsd4grml /media/stick0/boot/addons//
# umount /media/stick0
# mount -o iocharset=iso8859-1 /media/stick0
# rsync -rlptDH --inplace /mnt/boot/addons/bsd4grml /media/stick0/boot/addons//
# 

regards,
-mika-