Ok, I figured this out.

Here it is:
fullpath(builder.dbf') = C:\MMVISCOLLECT\BUILDER.DBF


>>>I notice that you still have the VFP8 folder in your PATH= in your config file. What if you change that to point to your VFP9 folder instead.
>>>
>>>--Brad
>>
>>Brad,
>>
>>Good catch, but didn't help :(
>
>To be honest, I've been having the same problem as you, though I have no intention of using _MemberData at all, because it bloats the VCX or SCX file with a huge XML string (in the _MemberData property of the class) and I believe makes the VCX/SCX non-backward-compatible to VFP8 because it has the potential of creating a property string longer than the 254-character maximum.
>
>The BUILDER.APP (defined by _BUILDER) program is responsible for calling the MEMBERDATAEDITOR.APP program if you choose the "Member Data Editor" menu option as Fabio had instructed. But mine does the same as yours... it calls the Form Builder instead.
>
>I don't know why... unless my BUILDER.APP is not quite working right for some reason. It's supposed to use the BUILDER.DBF in the WIZARDS folder and there is an entry for MEMBERDATA in that table, and it points to the correct APP, so I'm not sure what's going on.
>
>I did notice that if I change _BUILDER to point to HOME()+"MEMBERDATAEDITOR.APP" then the MemberData Editor does come up as it should, but I wouldn't recommend this, because then normal builders won't come up when they're supposed to.
>
>--Brad