@Playalot - Thanks. I added a reply to an existing bug thread on the EA Answers HQ forum. Seems like at least a few others have had a similar issue.
EDIT: I've discovered a rather clumsy workaround after many tries-
If stuck from advancing in a society try the following:
Travel to one of the clubs scheduled events. Make sure there are club members present and that it shows as such in the bubble with their name (Art Society Member etc). Leave the club. Then ask to rejoin. You won't lose any progress you've already made but it will start making the tasks work again.
Note: I tried leaving the Society from my Sims house (she lives at home in Willow Creek) and there were no members or even easels at the event. When i used the phone to contact/bring one of the members to the lot - they did not have the Art Society member designation under their name - so I couldn't rejoin. Luckily I hadn't saved. Next I traveled to the events and waited until I spied with my own eyes the club members and easels.