>>- the current form in the main exe has a container with a grid, which is coming from the subfolder\addon.vcx
>>- the grid has a column with tiny pictures (not .ico, .png, for which I had to use pictureval, otherwise they couldn't find the .png files inside the exe)
>>- doubleclick a row on the grid launches the form, with parameters taken from current row. Before launching the form I set classlib to ... in my.exe (without paths, will try with paths today)
>>- the form is a class in subfolder\addon.vcx (previously it was a .scx, and everything worked while the .scx was inside the exe, and it instantiated all it needed to from subfolder\addon.vcx), with a few containers and subcontainers from subfolder\addon.vcx, all based on classes which exist in the exe
>>- it bangs when creating one of those containers from subfolder\addon.vcx, the message is "classlib (parent of container) not found"; before that it readily creates a few objects based directly on classes from main exe
>
>First tries from me would be:
>
>1) trying to start next form via not included Prg instead of directly from subfolder\addon.vcx aggregated on Exe form (easy to check, but only 9% estimate of succeding)
>2) trying to start next form via included Prg instead of directly from subfolder\addon.vcx aggregated on Exe form (easy to check, but only 15% estimate of succeding)
>3) In exe, instantiate a class ONLY in subfolder\addon.vcx as property on screen, start second form from method of that class (harder to check, only 7% estimate of succeding but I'd do before 4)
>4) stimulate brain by repeated forehead/keyboard connections

Now the funny part, before (4) kicks in... I've removed the suspect object from the form class and am adding it via addobject(), wrapped up in try-catch, and bingo - the form shows up, without that object. The funny fact is that both that object and the form itself live in the same classlib and inherit from the same classlib-in-exe which allegedly can't be found. Other objects from that classlib are instantiated just fine on the same form.

At least I've narrowed it down.