after upgrading from PHP5.2.6 to php 5.3. it seams, I also have to reinstall the PHP memcache-module. So I downloaded the newest version of memcache (3.0.6) and followed this do
To answer my own question an for rising the intellectual horizon of @OZ_ and @martswite
an offline-installation of an pecl extension works like the following way:
1.) download the extension from http://pecl.php.net/packages.php
2.) there you get an .tgz file
3.) install the file:
pear install memcache-3.0.6.tgz