>>I have isolated the problem thanks to Naomi's tip : the use of a function (starting with an = sign) in a property (in the tag property more specifically). VFP 7.0 and follwowing seems to have problems with that.
>>
>>I'm still trying to understand with exactly goes wrong. I'll keep you informed if you want.
>>
>>Special thanks to Naomi but also to Yuri !
>
>You're welcome. It was discussed here few times, what's how I knew about that problem.

The exact problem was : properties blanked manually (not using the 'Reset to default' ... the (None) is bold) aren't correctly converted to 7.0 or 8.0.
The individual control can be opened and VFP comes up with an invalid property value error (which can be solved), but controls the inherit from such a control open with syntax error.