Hi Pablo,
The main problem with minigui are the following two:

First, minigui, unfortunately, did not keep a close touch with parent project (Harbour)
regarding the windows API. In Harbour we have the hbwin and some other libraries
(f.e. hbmisc, hbxpp et.c.). Those libraries are based on very robust and heavily tested
pieces of code. Now, many of the hbwin functions there exist in minigui but there are
implemented by their own (and in some cases, very aged) code.
If you'd ask me which one of the different implementations (Harbour's or minigui's) I would trust and would prefer,
well I'll let you guess..
Second, minigui (both variants, official and extended) suffers by the well known
(I'd say inevitable) "desease":
Plenty of "workarounds" and circumstantial fixes.
Saying this, I don't try to eliminate or undervalue the tremendous work that has been done
by the main minigui developers and all the remarkable contributors. I'm just spotting a fact.
Minigui is an exceptional and very succesful GUI library for Harbour compiler.
I like it and I do use it for a long time.
What I'm trying to note, is that when a problem arises, it is good to try to isolate it in accordance
to the parent project (Harbour) by seeking solutions that do not conflict or do not ignore relevant
solutions already implemented in Harbour.
That said, I think that Minigui needs a refreshing clearance of those "its own" API functions
and replace with those which there exist in Harbour with similar names.
As a I have mentioned, CallDll32 of minigui is (at least according to my tests) broken!
The same probably apply (not tested, though) for LoadLibrary/FreeLibrary/GetProcAddress et.c. functions.
It would be a good move to have those functions replaced by the
wapi_* equivalent functions
found into
hbwin library.
I know that's not an easy task, not to mention that it may break compatibility with existent code.
But again, trying to fix a not so good/outdated or perhaps buggy code, which conflicts with Harbour,
doesn't seem an optimum choice either.
Maybe the suggested replacement could be done by a step-by-step process.
That's my two cents.
best regards,
---
Pete