Can't make menus "first play," "File path not found -10010"

Hoping to get DVDitPro 6 working before the weekend.
I've corresponded with tech support, but haven't received a reply yet on my current problem (sent in 2 days ago). I trust they (Kevin) are working on it, but maybe someone here has had this before and resolved it: (it's now Friday afternoon)

I recently bought DDVitPro 6, and have been learning it for the past week+. The first time I tried to use the Simulator, with a menu (template) as First Play, I got this error message:
"File path not found -10010"
-- and nothing would play
If I made a video title First Play, it worked.
Finally I made my own menu background from a gfx, which DID play, and everytime after that all the menus did play in the Simulator. And all the test projects that had not played, now did.

This worked for two days, then on Wed. I got the dreaded error message again with ALL menus, every time, even self-created menus. My previous test projects, that had played, now do not in the Simulator. Once again, any VIDEO selected as First Play works fine, although when it ends (to return to the menu) I get the error message instead.

I removed and re-installed DVDit, that did not help.

I also tired unchecking "load media.. at start up" in the preferences, and made my own menu, but got the same error message.

The only thng I did to the computer between the day it was working and the day it stopped was to buy & load Sonic/Roxio's CinePlayer 3.2, which is a dvd simulator. I removed it once the problems started again, just in case.
But I don't think that would be the cause, since I had this error before.

Any help would be greatly appreciated.
Thanks!