Thank you for the info sorinfromtoronto!
Did what you suggested using the finder after selecting to show all hidden files and voila! Aperture is working again.
I am not sure whether it is only the FB problem. I did allow FB connection on all of my 3 Macs (2 iMac 27" and 1 MB AIR), but only selected the >allow< option on one machine when asked whether Aperture could access my contact library. That's the machine that had the Aperture crash - the others worked just fine!
Anyways, glad it works!
For those bashing Apple for the problems: Yes it is a nuisance, but did you ever think about the cost of Aperture and its updates vs. a similar product (i.e. Adobe Lightroom)? Even though we all hate problems in our software, I think it is still a pretty good value for the money!