:D Whoaow ! That's really fast, wasn't expecting this before some days ! Hurray !!!
Thank you ! (I'll put a small report here to confirm if things are fine on mine side)
*downloading*

So.. refering to this post, I still have issues #4, 5, 6, shall I contact support ? (every other issues are solved ! ;))

Okay !
I'm doing this right now ! As always, thanks for answers and helpfulness ! :)

Edit : I contacted support.
For people who may encounter same situation as me even with the version "setup_massive_assault_phantom_renaissance_2.1.0.3.exe", here is the temporary solution :

Here are issues I'm encountering :
1) When I select the Career mode in Single player, I click on which side I want to choose and... it crash (always).
2) Briefings on campaign mode : I can't access them at all. When I begin a campaign, the briefing screen appears (without text) and is "skipped" automatically to load the mission.
3) No voices in training levels (voices who explain things to do etc..)

Solution (who worked for me) :
a) Copy/past your game installation folder (the folder "Massive Assault - Phantom Renaissance" located in "C:\GOG Games\") somewhere else than the place it was initially installed (I tried to past it on my desktop for example).
b) Delete the game installation folder (but haven't uninstalled the game from computer)
c) Cut/past the copied folder (in desktop) where installed folder originally was (in "C:\GOG Games\". The game should be working perfectly now.

I don't know WHY it's working, but for me it's working.

Update 02/10/2015

GOG has released a update that has fixed the vast majority of the issues I reported in this thread, so I have removed the download links to my fixpack, if something new pops up I may create a new one.

Thank you Lord Kane & Splatsch, it worked!. I can now play the game at last. Just started a World War game. :)

Edit: aw heck it just crashed. It did get further than before though and I was able to play a few rounds before it happened. I'll try again and hopefully it will be more stable this time.

Have you tried the latest installer provided by GOG ?

no not yet, I'll give it a try now though and hope for the best.

nope, no luck. Still crashes as soon as I enter career mode and World War :(. Never mind I think I'll give up on this game, but thanks for your help.

I'm sorry to hear nothing really works for you :/
Are you sure this solution :

"a) Copy/past your game installation folder (the folder "Massive Assault - Phantom Renaissance" located in "C:\GOG Games\") somewhere else than the place it was initially installed (I tried to past it on my desktop for example).
b) Delete the game installation folder (but haven't uninstalled the game from computer)
c) Cut or past the copied folder (in desktop) where installed folder originally was (in "C:\GOG Games\"). The game should be working perfectly now. "

doesn't work for you ?
Have you tried to change the windows compatibility setting of the executable ? (may be can this help ?)

And you're welcome for the help :) It's always a pleasure to try to help !

Thanks Splatsch for all your help, I tried all those things you had mentioned, but nothing seemed to work. My only other option I can think of is to reinstall and try again whenever I get round to doing a full system OS install (maybe when I finally upgrade to Win 10, i'll give it another bash). I dunno mate, maybe I have a virus on my computer or some system files aren't what they used to be anymore... well, stranger solutions have appeared before :). Thanks again though and I'll be sure to get this game working somehow, sometime in the future heh, Cheers!.

I don't remember, have you tried to instal/launch it with admin rights and this kind of things ? With my solution, if you copied the installed game folder on your desktop, have you tried to launch it with the .exe on the folder on your desktop ?
If nothing works, I won't be able to help more I'm afraid.
You are welcome :) I hope you'll find a way to play it soon ! Cheers ! :D

You know what Splatsch. I reinstalled this not too long ago and lo and behold it worked without any problem haha. Have no idea what had changed as all those previous attempts met with no success and I did nothing but install and run this time and there's been no problems since. It's still a pretty fun game :D

Ahah, computers XD
At least, you can enjoy it now ! :D Glad to hear it ! As long as it works, it's great.
I really like the game too, so have fun and play well ;)