Install gstack.

Ubuntu AMD64 doesn't come with pstack/gstack, but it can be downloaded from other RPM distributions. Here are the basic instructions that I got to work:

http://www.google.com/#sclient=psy&hl=en&q=gstack+rpm+launchpad&aq=f&aqi=&aql=&oq=&pbx=1&fp=25a0b2344dc0e416

1. wget http://download.fedora.redhat.com/pub/fedora/linux/updates/13/x86_64/gdb-7.1-34.fc13.x86_64.rpm

2. sudo apt-get install rpm2cpio

3. sudo apt-get install gdb

4. rpm2cpio gdb-7.1-34.fc13.x86_64.rpm | cpio -idmv

These files will then be output in the current present dir -- you can then go 

5. Edit the gstack file to use #!/bin/bash instead of #!/bin/sh