Oracle 11g Linux says "database/install/unzip: not found"

Yesterday, I started to install Oracle Database 11g to Ubuntu 8.10, after downloading and unzipping the about-1.9-GB package of the software.
But when I run its installer (./runInstaller), I encountered error that says "database/install/unzip: not found".
The unzip executable file was actually exist, but the unzip could not work at all, preventing me starting installation of Oracle Database 11g for Linux.

I, as a novice of Oracle user, googled the error message many times. Finally I found the solution for this unzip-not-found problem: do not use the unzip which is contained in oracle package.

Instead of the oracle-given unzip, I created symbolic link to locally-installed unzip.

(in "database" directory)
mv install/unzip install/unzip.backup
ln -s `which unzip` install/unzip

After creation of the symbolic link, I could successfully start to install program!

However, this was just "start to install": so many problems were occured during install process, that I do not want to write these problems!!!11

Could oracle help me...