Going through Caroline's rigging tute and at some point in testing the rig and turning the TSM constraints off and on, under "Relationships>Bones" I've got about a dozen folder icons with various element names followed by this error message (e.g., "left Arm IK Error Loading String:5003")

So far everything seems to be functioning but I'm not sure why these are being generated. Any ideas?

Try...saving your character as a new name.

Okay, I did that. I think what may have precipitated this was that I had been saving successive models under new names, and may have opened an action that used an earlier model version that I then deleted. At least that's what I suspect. Everything seems to be functioning okay. I'll monitor the situation.

EDIT: It appears I've had Mirror Mode turned on for the last couple of hours. that may be the culprit.

Robert's the TSM guru but I have had this problem and so have others when doing everything correct.

This is a link to that topic.
http://www.hash.com/forums/index.php?showtopic=32122

I hope it helps you find the solution.

The one thing I do know is it has no adverse affect on the model.
It's just annoying to look at.

save, restart, reopen

That appears to have fixed it, but I have another newbie question: what does a folder icon with a question mark on it indicate? Inside the Relationship>Bones in the PWS there are folder with bone names and question marks on them.