I just have a small problem...
I can see the model with all the textures in the view of MED with no problem... However, in the engine I either see through the model or in some other models the texture shows in a messed up way....

I even tried to attach action to the model but I still get the same problem....

dont use alpha channels in skins

Well these are all ready models .... Is there anyway I can deactivate alpha channels by script or inside the editor ??
I even tried to uncheck the "alpha" from the skin but doesn't help...
One more question ... what's the benefit of Alpha channels in games??

Alpha channels are kind of like a secret place in a picture to store info.
In our case we generaly use skins with alpha channels to provides models with the ability to be translucent.
And, we use skins with alpha channels to provide terrains with the ability to be translucent in areas where other skins can sort of bleed through.
That way certian areas can be grass and other areas can be different textures like gravel or clifs or sand etc.

So, what do you mean that your models are "ready models"?
It seems to me, if they are "Ready" they wouldn't be giving you grief...

Seeing that you are kinda new to this, I suggest that you have a close look at the 3DGS manual.
Go into the manual and do a search for "Entities" that page is very important and can answer many of your questions...

@TerraSame ... Thanks sir for the explanation .... It really helped ....
Now what I mean by "Ready" is that it was not modeled and textured by me Excuse my language

I just added to my first response.
Please see the last two lines...

Your last response did not answer my question...
Were your models created specifically for 3DGS???

I read part of "Entities" page in the manual already... However, I guess I have to read it all....
For the model.. I am not talking about a specific one so not all of them were created specifically for 3dgs ... I have some free models websites... But one of the models I am talking about which was created by a 3dgs user is the building that rvL_eXile created few days ago...
http://www.opserver.de/ubb7/ubbthreads.php?ubb=showflat&Number=337356&page=3

You will not only want to read it all, but you will want to refer to it often...
As well, you will want to review it after new revisions of the 3DGS software
are released because sometimes there are changes...

If you care to, you may take a screen shot of the problem model and send me the
pic and a copy of the exact model and I will review it in my personal under construction game.

One thing, you said that you reviewed the model with the engine...
Their are three ways to do that...
I wonder if your review is by actualy running an exe file...
ie. running a game???

Alpha channel is for transparency, you just need to go to skin settings and check 24-bit then click OK and save.

Somewhat older video but explains these steps:
http://www.youtube.com/watch?v=7Lxft1ML05U

Translucent vs transparent... Depends on the language and version...
C++ or C-Light and A6 or A7 & A8
My expanation has been based on a combination of both Photo Shop Adobe and Jasco Paint Shop Pro along with the 3DGS definition...