I had a similar problem, though the error message I got was from ACR. I asked about it on the Simbology forum --
http://www.simbology.com/smf/index.php?topic=3645.0The error was caused by one of my sims not having an aspiration. I used TJ's blender to give her an aspiration (SimPE didn't work) and that fixed the problem. You might check their aspirations to make sure they both have one.