Roger:

Sometimes strange or sluggish behavior by your operating system can be rectified by reconstructing the invisible desktop file that keeps track of where all your files are located. I'm afraid in your case this may do no good, but I'll tell you how to do it anyway.

First, one mildly harmful side effect. Rebuilding the desktop erases any written comments stored in the Get Info boxes for all files on your disk. This is not a problem for most people. In fact, you hardly ever see these comments because they tend to get erased sooner or later anyway.

The procedure is simple. Just boot your machine while holding down both the command and option keys. If you have a long start-up sequence, you may have to hold the keys down for thirty seconds or so. EVENTUALLY a dialog box will appear and ask if you are sure you want to rebuild the desktop. Answer yes. The disk will spin for a minute or two. And that's all there is to it.

I just rebuilt mine for the first time in over a year and it made a noticeable improvement in the time required to open large folders.

But, as I said, this is probably not going to help you, Roger. I suspect that your aging version of Lightspeed C simply doesn't like the new operating system. Sooner or later you are going to have to upgrade your Lightspeed C.