Resolution - just for peoplewith a similar problem who find this thread by searching the forums.  Once MagnusGreel alerted me to the Windows User Account Control (UAC) issue, I was able to find resources to help, including searching the forum threads for UAC. 

Essentially, in my case, Windows would not allow Poser 8 to write files to my drive because I had installed Poser 8 in thedefault c:programs directory.  My Windows UAC settings prevent writing to those folders unless the administrator gives permission.  For some reason, Poser wouldn't prompt me to ask for permission.

My choices include but are not limited to

1. uninstall Poser and reinstall it in the My Documents folders where permission to write is not required.

2. only save my own work to runtimes created in the My Documents folders

3. use the Windows control panel to turn off the security settings in the User Account Control, but then I would face greater risk of getting hacked

4. leave everything where it is but run Poser as the administrator

For the moment, I am running Poser as an administrator by right-clicking on my Poser icon and choosing that option.  It has resolved the missing file mystery.

Furthermore, the UAC settings had also prevented me from uncompressing my obz files (in a way that I could find them again).  I have successfully retrieved the obj's now for morphs, etc.

My UAC settings are still set at relatively high security, I can create and find files in the Poser main directory, and Poser seems to be working well with C8 again.

Big thank you to MagnusGreel and the other helpful forum people.