Lucas,
The bug you reported me regarding RichEdit made me realize that there is code in FWH that has not been properly adapted to 64 bits:
Everytime we use the extend system to send or receive a handle, we have to use hb_parnll() and hb_retnll(). This is due to the fact that handles in WIN64 can be larger than in WIN32, so I have started searching for all of them and checking that they are fine. Up to now I was most focused on made FWH 64 bits apps work properly and missed that important part too.
I have already modified many FWH C files to properly use hb_parnll() and hb_retnll(). I have not finished with all of them, but I prefer to make the changes progressively in case that some code could bring a problem. In fact, I think that everytime we supply a HWND, HDC, HBITMAP, HBRUSH, HFONT, etc (any handle) we could simply call hb_parnll() even for 32 bits apps, but I am not sure yet 100% if this could have any side effect. Same applies for hb_retnll().
So on a first stage the idea is to inspect all the code, locate places where those handles are not properly managed in 64 bits and once that process is completed, we could consider to call hb_parnll() always (though that just would simplify the source code but would not benefit our apps).