Never mind - found the solution (for me anyway) here: http://www.talkaboutsoftware.com/group/microsoft.public.fox.programmer.exchange/messages/179275.html

I ran "Clean Up Project" before recompiling in VFP9 and that seemed to fix the problem.

>Did you ever figure this out? I'm just now trying to upgrade an app from VFP8 to VFP9 and am having the same problem. The PJX/PJT is fine if I rebuild in VFP8 - but when I try VFP9, I get the invalid or missing problem.
>
>>Hello
>>
>>I am trying to compile my vfp7 application under vfp9 Beta but I am getting the error that the application PJT is missing or invalid. is this a known bug or I am doing somehting wrong.
>>
>>Mo