[Koha] Help please! we have problem after upgrading ubuntu from 11.10 up to 12.04

[Деловой Библиотекарь]

Hi there!

My name is Nikolay, I'm from Moscow, Russia, we use Koha LS. Last time ago koha start working  very slow. We did upgrade ubuntu server  up to 12.04 and new when we try connect to Koha we have next: 

Software error:
Can't locate Cache/Memcached.pm in @INC (@INC contains: /usr/share/koha/lib /etc/perl /usr/local/lib/perl/5.14.2 /usr/local/share/perl/5.14.2 /usr/lib/perl5 /usr/share/perl5 /usr/lib/perl/5.14 /usr/share/perl/5.14 /usr/local/lib/site_perl .) at /usr/share/koha/lib/C4/Context.pm line 86.
BEGIN failed--compilation aborted at /usr/share/koha/lib/C4/Context.pm line 98.
Compilation failed in require at /usr/share/koha/lib/C4/Auth.pm line 28.
BEGIN failed--compilation aborted at /usr/share/koha/lib/C4/Auth.pm line 28.
Compilation failed in require at /usr/share/koha/opac/cgi-bin/opac/opac-main.pl line 22.
BEGIN failed--compilation aborted at /usr/share/koha/opac/cgi-bin/opac/opac-main.pl line 22.

What we must to do to fix problem? I am VERY new in *nix, so please be polite 😊

Thanks for help!