Whenever a player has unexpected CTD's as your having the first thing to check is your
own game setup (believe me, if RFB 2.0 was that buggy we would have found it out before now!).
Remove the mods from JSGME "Activation" and run the apps "Tasks...." menu feature "Compare Snapshot". This will compare your original stock game files (when you first installed JSGME to a freshly installed game), to the game files you have now. Didn't take an original "Snapshot" of your clean game files when first adding JSGME?
Do a complete removal/re install of the game, following the steps lined out
HERE. Add a fresh JSGME to the game, then take the needed "Snapshot" for future use. Re download the RFB mods (could be something in your download that's causing problems), then try it all over again.
Don't forget to remove your "SH4" folder, found in your "Documents" folder of your computer. This folder holds your personal game options (like choice of screen resolutions, or manual/auto targeting selection, etc.), and also keeps track of any saved game points you or the game makes. Get rid of it....the game will make a new one the next time it starts. Yes, you'll have to make new choices for the options, but then again, things aren't working out for you now?!
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You say your Steam download is version 1.5 of the game. Does it read like this, at the bottom of the stock "Main" menu screen:
Sorry to seem so trival, but there's been all kinds of issues with just what version of the game Steam is selling players? Least wise with the first download of Silent Hunter 4........it's reported they give you version 1.3 (a poor excuse of the original version of the game....they should have at least given you v1.4). You don't get bumped up to 1.5 until you purchase the U-Boat Addon, at an additional cost.