Thanks, Discoseven, I appreciate you taking the time to test this for me.  I think what's happening is that a script I'm using is corrupting the scene somehow, adding something in that Carrara can't handle.

I've been keyframing the figure in poser, then using this short script from PhilC here:

http://www.renderosity.com/mod/forumpro/showthread.php?thread_id=2736524

to add keys to the whole figure.  I then switch the figure's limbs from IK to FK in poser since Carrara can't handle Poser's IK.

When I just used the walk designer, the scene saves and load ok in Carrara, but when I use Phil's script it must add something that Carrara doesn't like.  I'm trying to find out what now.