Hello Malone and Epervier
i apologize for your lost time: i found the explanation : i had flown a Bf-109 under slovaquian colours sometime before installing mods...
When i began installing mods with 4.12, i didn't care about country name or even axis/allies camp and didn't notice Slovaquia was still there !
i just quickly tested the aircraft in flight, their skins and sometimes their weapons.
It didn't cause any problem with all other aircraft : D520, LeO451, MB152, CR714, but for some reason it did with VG33 !
i since have checked that all other allied or axis nations (Germany, Italy, Finland, ect ...) do not cause any problem for VG33; just Slovaquia !!! (for a reason quite mysterious for me !)
So the addition of the VG-33(SK) directory is only necessary if ones want to fly the aircraft under slovaquia !
(Malone could thus probably recreate the problem easily with his install, just for the "pleasure" of trying a slovaquian flight !)
This of course is a quite minor bug; the really interesting update should be to include Birdman fixes in the VG33 upload.
(working in 4.12 as well)
Sorry for your lost time, this is the first time i meet problem with country name !
Anyway, great thanks for your help, without it i would probably have dropped VG33 in 4.12 before finding the explanation !

Jantot