if those fail to produce any updates, try allocating more RAM to MS-Word 2001.
I assume you have "Virtual Memory" turned OFF and "File Sharing" turned OFF?
also, install from CD if you have it, or the next best FRESH copy of the PDFWriter Chooser extension. They can get corrupt sometimes as can the Chooser itself.
If all above fails, try a fresh install of the OS (it will rename your old system folder so you won't lose it) and then just install the PDF extension and try out Word 2001 again with this new system. If it still crashes, I would suggest there is a Word issue.
PS - When you are done testing, rename the fresh sytstem folder to FRESH System Folder, Rename the "System Folder Copy" that was created by the fresh install to "System Folder", take the Finder file out of the FRESH System Folder, open and close the System Folder to get it blessed again (you'll see the little icon on the folder) - carefully check all the steps and then re-boot
Then you can delete the FRESH System Folder and Finder file and go back to your current System.