old.ppta constantly being created

Hi - I have worked with pptx and ppta files for quite awhile and understand how the old.ppta files get created. However, for some reason, I am now getting a new .ppta file (and, consequently, a bunch of -old.ppta files) every time I update or preview and interaction or quiz from the pptx file. None of the situations below (from the Knowledge Base) apply to my situation, and I have tried repeatedly to rename the old.ppta to the regular .ppta, to no avail. I can only suspect that something is locking the ppta file, but I have no idea what - there are no new programs on my computer - I have not done anything differently since creating these files over a month ago. Help!

1. If the PPTA file becomes locked by another service: If another computer service (for example:  a backup service) accesses the PPTA file while you are working with it, Presenter may not be able to update the file with new information.  In this scenario, Presenter will rename the PPTA file to <presentation>-old.ppta, and a new PPTA file will be generated. JB: I don't know what computer service this could be on my computer - I have no backup service.
2. If a user does a “Save as” and saves over an existing PowerPoint file with a PPTA file: Whenever a user does a Save as, Presenter will also copy the PPTA file to the Save as Location. This can cause a conflict if there is already a PPTA file in that location. Rather than overwriting the file, Presenter renames the file to <presentation>-old.ppta. JB: I have never done this.
3. If Presenter upgrades a project from Presenter 5 and a PPTA file already exists in that location: If a PPTA file already exists, Presenter will change the name of the file to <presentation>-old.ppta and create a new one. JB: I have always used Presenter '09.
4. If you have a PPT (2003 or earlier) and PPTX (2007) file in the same folder with the same name: If you have a PPT and PPTX file in the same folder withe the same name, Presenter will want to name the PPTA file the same regardless of which file you are working on. If there already is a PPTA file in the folder that is not associated with the PowerPoint file you open, Presenter will change the name of the file to <presentation>-old.ppta and create a new one for the opened PowerPoint file. JB: Not applicable.
5. A user moves a file outside of PowerPoint, and there is a PPTA with the same name as the PowerPoint file in the target directory: If Presenter detects a project is moved outside of PowerPoint, it will copy over the PPTA to the current directory (provided you have write permissions to that directory). If there is an existing PPTA file in that location, Presenter will change the name of the file to <presentation>-old.ppta and create a new one. JB: Not applicable.

Restoring the connection between the original PPTA file and your PowerPoint file

In the event that a <presentation>-old.ppta file is created or if you have renamed or relocated your PowerPoint file (thus breaking the link to the PPTA file), you can easily reconnect the original PPTA file with your PowerPoint file, which will restore your missing audio resources. Here’s how:

1. Ensure that the PowerPoint file and the original (or “-old”) PPTA file are located in the same folder.
2. Remove “-old” from the PPTA file (if applicable), or rename the PPTA file so that it has the same file name as the corresponding PowerPoint file.

JB: Tried this repeatedly and it never worked. An old.ppta is still created each time I update or preview an interaction or quiz from the .pptx. I have also rebooted etc.