Have you considered using aptitude ? it's better at resolving dependency issues..
aptitude update
aptitude keep-all (only needs to be run the first time you use aptitude, you should not use apt-get any longer after you switch to aptitude)
aptitude install synaptic
Not sure why it's telling you that libsasl2 is not installable, those packages are in the Etch repositories..
Code:
default@debianetch:~$ apt-cache policy libsasl2
libsasl2:
Installed: 2.1.22.dfsg1-8
Candidate: 2.1.22.dfsg1-8
Version table:
*** 2.1.22.dfsg1-8 0
500 http://ftp.uwsg.indiana.edu etch/main Packages
100 /var/lib/dpkg/status
default@debianetch:~$ apt-cache policy libsasl2-2
libsasl2-2:
Installed: 2.1.22.dfsg1-8
Candidate: 2.1.22.dfsg1-8
Version table:
*** 2.1.22.dfsg1-8 0
500 http://ftp.uwsg.indiana.edu etch/main Packages
100 /var/lib/dpkg/status
default@debianetch:~$ apt-cache policy libldap2
libldap2:
Installed: 2.1.30-13.3
Candidate: 2.1.30-13.3
Version table:
*** 2.1.30-13.3 0
500 http://ftp.uwsg.indiana.edu etch/main Packages
100 /var/lib/dpkg/status
default@debianetch:~$