So you are having trouble updating just the virus definitions? If so, this might help -
Open the file /etc/freshclam.conf (as root) and look for a line, it is probably line 6 or so, that has "Example" in it. Comment out this line by placing a "#" in front of it (without the quotation marks). Save the file and see if it updates now.
I may be wrong, but do not try to update anything but the virus definitions. When there is a new GUI update, it is done through synaptic and not the program.
Hope this helps.
Desktop: AMD 3.6ghz X4, Gigabyte MB, 8GB ram, Multiple PCLOS's, 18.104.22.168-pclos3.pae.bfs
Server: Intel 3.4ghz X2, 4GB RAM, SATA, gnome2, *.pae.bfs, Headless, Servers: LAMP, FTP, Samba, Print, PXE, BT
HTPC: Phenom II X4 2.8ghz, 4GB Ram, 1TB SATA, PCLinuxOS-KDE, NVIDIA N220GT HDMI, *.pae.bfs