Comment 7 for bug 174570

I found the following workaround on the Ubuntu forums: http://ubuntuforums.org/showthread.php?t=530115

config file is at '/root/.synaptic/synaptic.conf'

If you are getting hang-ups I would relocate its entire config folder
and start it after in a terminal to read any output.

Code:

~ $ sudo -s
# cd /root
# mkdir .backups
# mv .synaptic .backups/
# exit
~ $ gksudo synaptic

This didn't work for me since the proxy setting still wouldn't change, so I used "vi" to edit the configuration file at: /root/.synaptic/synaptic.conf and changed the setting for "useProxy" from "1" (which means use the proxy) to "0" (which means do NOT use the proxy).

Unfortunately, I have to edit this file to use the proxy when I'm at work, and then edit it again when I return home. I don't know why the GUI crashes each time I try to use it to make this change.