Comment 3 for bug 150434

Well you need to retitle your bug and leave out the LIVECD part, it is very confusing.
The expected behavior for synaptic is to not run if dpkg has a lock, if for some reason dpkg dies un-expectedly its lockfile will remain, preventing subsequent attempts to use apt, aptitude, dpkg, synaptic, add/remove programs from running. Deleting the lockfile (/var/lib/dpkg/lock) will fix this.