John, I had spelled PyExcelerator with a capital P, but it worked just fine. I then checked the directory it was installed in, and found it read C:\Python24\Lib\site-packages\PyExcelerator. As soon as I changed the directory name to C:\Python24\Lib\site-packages\pyExcelerator, my programs stopped working! I then changed PyExcelerator to pyExcelerator in my programs and they worked alll over again.
After much playing around, I discovered that I had incorrectly indented the call to writeData, so that it ran only once, after a loop was exited, and not for every iteration through the loop. Thanks Thomas Philips -- http://mail.python.org/mailman/listinfo/python-list