this is the log
WARNING: ZCS is currently only supported on Ubuntu Server 6.06 and 8.04 LTS.
You are attempting to install on Ubuntu 8.10 which may not work.
Support will not be provided if you choose to continue.
Do you wish to continue? [N] y
Operations logged to /tmp/install.log.6369
Checking for existing installation...
zimbra-ldap...NOT FOUND
zimbra-logger...NOT FOUND
zimbra-mta...NOT FOUND
zimbra-snmp...NOT FOUND
zimbra-store...NOT FOUND
zimbra-apache...NOT FOUND
zimbra-spell...NOT FOUND
zimbra-proxy...NOT FOUND
zimbra-archiving...NOT FOUND
zimbra-convertd...NOT FOUND
zimbra-cluster...NOT FOUND
zimbra-core...NOT FOUND
PLEASE READ THIS AGREEMENT CAREFULLY BEFORE USING THE SOFTWARE.
ZIMBRA, INC. ("ZIMBRA") WILL ONLY LICENSE THIS SOFTWARE TO YOU IF YOU
FIRST ACCEPT THE TERMS OF THIS AGREEMENT. BY DOWNLOADING OR INSTALLING
THE SOFTWARE, OR USING THE PRODUCT, YOU ARE CONSENTING TO BE BOUND BY
THIS AGREEMENT. IF YOU DO NOT AGREE TO ALL OF THE TERMS OF THIS
AGREEMENT, THEN DO NOT DOWNLOAD, INSTALL OR USE THE PRODUCT.
License Terms for the Zimbra Collaboration Suite:
Zimbra - Zimbra Public End-User License Agreement, Version 2.1
Press Return to continue
Checking for prerequisites...
NPTL...FOUND
sudo...FOUND sudo-1.6.9p17-1ubuntu2
libidn11...FOUND libidn11-1.8+20080606-1
libpcre3...FOUND libpcre3-7.6-2.1ubuntu1
libgmp3c2...FOUND libgmp3c2-2:4.2.2+dfsg-3ubuntu1
libexpat1...FOUND libexpat1-2.0.1-4
libstdc++6...FOUND libstdc++6-4.3.2-1ubuntu11
libstdc++5...FOUND libstdc++5-1:3.3.6-17ubuntu1
libltdl3...MISSING
Prerequisite check complete.
Checking for standard system perl...
perl-5.8.8...Unable to find expected perl-5.8.8. Found version 5.10.0-11.1ubuntu2 instead.
###WARNING###
The suggested version of one or more packages is not installed.
This could cause problems with the operation of Zimbra.
Do you wish to continue? [N] n
Exit? [N] y
Exiting.
my@my-desktop:~/Documents/zcs-5.0.10_GA_2638.UBUNTU8.20081003052843$ sudo apt-get install libltdl3
Reading package lists... Done
Building dependency tree
Reading state information... Done
Package libltdl3 is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source
E: Package libltdl3 has no installation candidate
Regards