If you happen to have Fallout New Vegas that you have purchased in Poland, Czech or Russia, you WILL come across problems when trying to run the game with 4GB Fallout New Vegas program, which allows for the game to ustilise 4 GB of your RAM. The problem manifests itself with launching the Game Launcher instead of the game itself when you run fnv4gb.exe. Your INI files will be reset each time and if you use Mod Organizer, it won't work at all, as the game will not see any mods (i.e. the MO's virtual Data folder). This is due to the fact that English and non-English versions of the game have different Steam App ID reference numbers, and FNV 4GB has an English one hard coded in it.
To solve the problem you will need to create a shortcut for your fnv4gb.exe file. For Windows users: right click the file and select "Create Shortcut" from the context menu. A new file (shortcut) will be created. Right click it again and select "Properties" from the context menu. Properties window will be displayed. Navigate to "Shortcut" tab and add the following in the "Target" field, at the end of existing entry, without the quotation marks: " -SteamAppID 22490" (there is a space in front). So in my case, the entry in that field looks like this:
"E:Program Files (x86)SteamsteamappscommonFallout New Vegas enplczrufnv4gb.exe" -SteamAppID 22490
(The quotation marks ARE required for the first part, this is due to the spaces in folder names, but let's not get into too much details. The quotation marks around the SteamAppID argument are not requited).
If you use Mod Organizer, there is no need to create a shortcut. Instead add the following without the quotation marks to the Arguments field in the FNV4GB.exe executable in MO: "-SteamAppID 22490" (note there is no space now)
Voila, all done, your game will run correctly now!
Thanks to RoyBatterian, the uploader of updated 4GB Fallout New Vegas file, that can be found here.