I can't install php5-apc:

~# apt-get install php5-apc
Reading package lists... Done
Building dependency tree
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies:
 php5-apc : Depends: php5-common (= 5.3.19-1~dotdeb.0) but 5.3.8-2 is to be installed
E: Broken packages

Have fresh Debian 6 and

deb http://packages.dotdeb.org squeeze all
deb-src http://packages.dotdeb.org squeeze all

in source.list.

P. S. I'm not very experienced—just trying to set up a server by the tutorial.