Taht's odd
----------- parse scripts ----------
0 script files
Could not find version string for script files
Apparently the game can't find the script files (0 script files) but
Added packfile ./base/0ufos.pk3 (136 files)
The pk3 containing the scripts was added successfully, don't know what the problem might be, but you could try to unpack the scripts and see if that works:
Extract the contents of
0ufos.pk3 to
<ufoai dir>\base\ufos, you might need to create the
'ufos' directory as it most likely doesn't exist, pk3 files are simple zip files, so just about any archiving utility should be able to extract the contents.
I'm not a windows user, but I recall that windows doesn't like it when you modify program files/directories, so if you installed UFO:AI to the default location you might need to jump some hoops before windows will let you change things, if that's a problem you might try to put the extracted files into
C:\Users\byron\AppData\Roaming\UFOAI\2.5\base\ufos instead