We produced a strange behavior since nsis version 2.42.
The installer window does not open when the installer is created with version 2.42 or 2.43. This is not a general behavior. We have created many other installers which works fine. A script which produces the error is attached.
Switching back to version 2.41 everything is ok.
When you compile the file DataDirectorySetup.nsi an installer DataDirTest.exe is created; the installer executable doesn't work when created with nsis version 2.42 and 2.43.
Additional comments can be found inside the script file.
DataDirTest
It's because DataDirectory is not referenced and is zeroed out. WordReplace's code is actually in that function because you've used it there first. For now, you should put the first WordReplace call somewhere else or use that function.
Fixed for 2.44.