Oh, I just remembered there was a problem with installing IUB1.03 via JSGME because by default the IUB installer included an extra folder layer. You may like to ensure that the mod path is:
\SilentHunterIII\MODS\IuBv103\data\ and NOT
\SilentHunterIII\MODS\IuBv103\Improved U-Boatv103\data\
Just found
this thread on the subject which outlines the steps to take to fix.