[UAI] Hard problems in AI

[Rich Neapolitan]

Dear Colleagues,
I was wondering if anyone knew of a list of hard problems in AI, or if 
anyone could just inform me of the ones of which they were aware. For 
example, inference in Bayesian networks has been shown to be #P-complete. 
So this is a hard problem in AI.
Thanks much and have a nice holiday,
Rich