make sure no files on the hard drive have read-only access and make sure your save game path is not pointing to either a remote network location of indeed to a CD.
That's all I can think of. Sorry
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The Unofficial Space Empires 4 Mod Utility V1.7 (Revision 3)
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Download as a .ZIP <
HERE>
Download as a .RAR <
HERE>
Download as a .ACE <
HERE>
Check a Screenshot of it<
HERE>
Check an Alpha Shot of my Mod Editor (Unreleased) <
HERE>