Thanks, Tarun. Yes, I've looked at them--but there is something else here, that I've just discovered. I run several XPs on this single computer, on a multi-boot system using 15 partitions. It just occurred to me to try a different XP. I tend to work from only one for a few days at a time.
In the other XP--on the same computer--no problem at all, with CC 1.19.108. It is still working perfectly, as it always used to.
So, the problem is with my setup on the first XP--which actually seems to be my best-setup XP! Now, the really big difference between those two XPs is mainly in the Startup Programs array. The one at fault has a beautifully tweaked system--ha ha! beautiful, but obviously it contains the problem! I can't guarantee it isn't something else, but I'll look there.
And I have found that System Security Suite (3 S) does the same thing--it takes 100% of my CPU, which is not a problem in itself UNTIL I give it its second command, which causes the same freeze.
No other programs show any problems. Both CCleaner and SSS are system cleaners, so I think it's in there somewhere. But the two registry cleaners I use are fine.
Very interesting. It's got to be something to do with Startup, so the next thing I'm going to try is to move CCleaner to a different starting location and try from there.