I am using Ubuntu 10.04 Lucid Lynx Alpha and I encountered this while installing ltsp-server. The package being configured was ldm-server.
I was installing an application and Synaptic Package Manager just froze forever while configuring a package. I had to shut it down using sudo killall synaptic. Then, when I tried to launch t again, it would come up with “Unable to get Exclusive Lock” message. When I tried apt-get from Terminal, I got /var/lib/dpkg/lock – open (11 Resource temporarily unavailable).