Thanks for the replies and suggestions.
I solved it with an older Knoppix 3.2 I still had around (old versions se
em
no longer available on the net). Recreating grub however failed and was d
one
with the SL5 LiveCD.

It seems that newer distributions add the resize_inode and ext_attr featu
res.
If SELinux is enabled (probably the case on the LiveCD?) all written file
s
get the extended ACL entries. Maybe a LiveCD without SELinux and removing

(with debugfs) the attributes could help but I didn't try that.