So i downloaded the Enhanced shaders ENB(Nevada skies version) and ,for a brief moment,everything turns transparent and then comes back to normal,i understand its not a too grave issue but its annoying as hell,can someone help me?

Do you have Steam enabled in-game? If so, this will happen if one of Steam's pop-ups comes onto the screen (like someone messaging you or an alert that a friend is playing a game).

yes i have,so its steam tha is making my game go transparent?

I would say that is your problem. Disable the steam overlay in-game and see if the issue occurs at all.
Steam does it to my ENB all the time in NV, but I keep it on so I can take screenshots.

k friend ty for helping me out + 1 for you

Anytime bud Lemme know if the problem continues still!

dude if you plan on using nevada skies and ANY ENB for that matter use this to help performance

4GB New Vegas Updated
http://www.nexusmods.com/newvegas/mods/55061/?

this is essential in my opinion and can't imagine playing without it.

yeah i have it, i even use a custom launch command on NMM do i can start my game with it ass well as organize and install my mods

Oh ok just thought I'd suggest that because that also tends to be a problem with people and ENB's.

If you're still having the issue, disable Anti-Aliasing and Anisotropic Filtering in New Vegas' launcher (or the appropriate .ini if you launch from NVSE or FOMM/NMM). ENB forces it's own AA settings, so having it enabled in the game itself on top of it being enabled in ENB can cause weirdness - most notably transparent textures. There's also something about disabling a lot of setting for Water and Multisampling, but that may have just been Onix so don't quote me on it.