Among the 6 or so deaths that used to occur following smallpox vaccinations, what were the CAUSES of those deaths?

I wondered about that, too. I think they were in immunosuppressed individuals who ended up with systemic vaccinia disease. Those with T-cell dysfunction are at particularly risk.One who was described in the broadcast was an undiagnosed HIV-positive soldier who was vaccinated per routine. Of course, there have been "contact" cases of vaccinia, eg, infant of a recently vaccinated soldier who had inadvertant contact with the vesicles of the vaccine site, and ended up with severe (not nec fatal) disseminated vaccinia -- which is never as bad as smallpox, again, according to the broadcast.
Any other respondants out there? I'm no expert...

http://www.bt.cdc.gov/agent/smallpox/vaccine-safety/adverse-events-chart.asp

This link gives the CDC list of the causes of adverse reactions in the 1960s. Before HIV and presumably when fair less immunosuppressedpersons were around.

Eczema - allergic rash
Generalized - blisters all over
Autoinoculation (Eyes and Mouth especially)
Encephalitis can be severe
Death of tissue can occur