First, what the hell is Kpt.Lehmans MOD?
Can you point me to it?
Ok, so all the GWX files are 100%, which means the problem is with your installation of SH3 1.4b.
1) Use windows add/remove programs to uninstall SH3.
2) Delete the SH3 folder in My Docs.
3) Delete the SilentHunterIII Program folder found at C:/Program Files/Ubisoft/......
4) Reboot.
5) Reinstall SH3 1.0 from the game disk (FYI, if the game is new it maybe patched to 1.4 already, you can check by looking in the bottom right cnr of the main menu).
6) Run the SH3 1.4 patch (it will say 1.3 when installing, don't worry about it).
7) Reboot.
8) Now run GWX.exe to start the installer (make sure all GWX2 files are in the same location).
Let me know if there is an error report from the installer. Look for txt files on your desktop.