innanzitutto grazie per tutto l'aiuto
nel file sources.list ho questo (come default)

#
# /etc/apt/sources.list
#


#
# lenny
#
deb http://debian.fastweb.it/debian/ lenny main contrib non-free
deb-src http://debian.fastweb.it/debian/ lenny main contrib non-free

#
# Security updates
#
deb http://security.debian.org/ lenny/updates main contrib non-free
deb-src http://security.debian.org/ lenny/updates main contrib non-free
deb http://download.webmin.com/download/repository sarge contrib


da questo file io avevo cambiato la riga
deb http://debian.fastweb.it/debian/ lenny main contrib non-free
con
deb http://archive.debian.org/debian/ lenny main contrib non-free
(credo sia l'unica riga da dover cambiare, o almeno cosi leggevo online)
ma poi mi da il messaggio
Package curl is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source
E: Package curl has no installation candidate
se provo colo con sudo apt-get install php5-curl
invece mi dice
E: Couldn't find package php5-curl