Upgrading error

Upgrading error

When I do apt-get update // apt-get upgrade i received this error whatever
I do:
root@debian:~# apt-get upgrade
Reading package lists... Done
Building dependency tree
Reading state information... Done
You might want to run 'apt-get -f install' to correct these.
The following packages have unmet dependencies:
curl : Depends: libcurl3 (= 7.26.0-1+wheezy3) but 7.21.0-2.1+squeeze2 is
installed
multiarch-support : Depends: libc6 (>= 2.13-5) but 2.11.3-4 is installed
E: Unmet dependencies. Try using -f.
root@debian:~#
This is not my server so I don´t know what is installed inside, the only
thing I know is that I need to upgrade the php from 5.2 minimum to 5.3.
The told me that Zend Server is installed but I don´t know which version
either. The first thing I tried is this and everytime I get this error.
cat /etc/issue says: Debian GNU/Linux 6.0 \n \l