I decided to investigate and test things out before taking the step of reporting a bug, and I have found that today Text Antialiasing, on or off, makes no difference to running a preview/debug instance.
Today removing 45 or so small, about 1.1K each, sprites off the layout makes the difference.
I also note that Construct ties up an additional 200MB of RAM after each Preview/Debug instance, and explorer.exe is tying up 50% CPU after the first Preview/Debug instance. Shutting each of these processes, construct and explorer, is necessary to release the resources.
I think my XP may be screwed and its time for a re-install...