I've installed Gnome using these repositories :

deb http://security.debian.org lenny/updates main contrib non-free
deb http://ftp.de.debian.org/debian lenny main contrib non-free
deb http://ftp.de.debian.org/debian stable main contrib non-free
deb http://security.debian.org stable/updates main contrib non-free

The problem is that,for some reason,the package gnome-orca hasn't been installed. Gnome is started anyway,but not in full mode. To fix this problem,I've activated all the original knoppix repositories and I've written :

apt-get -f dist-upgrade

at this point due of this error the upgrade process is stopped :

root@Microknoppix:/usr/share/man/man1# apt-get -f install
Reading package lists... Done
Building dependency tree
Reading state information... Done
Correcting dependencies... Done
The following packages were automatically installed and are no longer required:
mesa-utils libdecoration0 python-numeric libdns43 libcdio7 compiz-plugins
libisc44 compiz-core
Use 'apt-get autoremove' to remove them.
The following extra packages will be installed:
The following NEW packages will be installed:
0 upgraded, 1 newly installed, 0 to remove and 289 not upgraded.
510 not fully installed or removed.
Need to get 0B/2014kB of archives.
After this operation, 7930kB of additional disk space will be used.
Do you want to continue [Y/n]? y
(Reading database ... 127024 files and directories currently installed.)
Unpacking gnome-orca (from .../gnome-orca_2.24.4-1_all.deb) ...
dpkg: error processing
/var/cache/apt/archives/gnome-orca_2.24.4-1_all.deb (--unpack):
trying to overwrite `/usr/share/man/man1/orca.1.gz', which is also in
package orca
dpkg-deb: subprocess paste killed by signal (Broken pipe)
Errors were encountered while processing:
E: Sub-process /usr/bin/dpkg returned an error code (1)

what can I do ? Thanks.