I wanted to share my progress:

I found out that the StarsHostEditor.dll is a .NET assembly... jackpot! (C# is easily decompilable). Using .NET Reflector + FileDisassembly, I found a Decryptor class:

http://pastie.org/pastes/9343482/text

I haven't done too much analysis, but so far it looks like it reads in a 'block' from the file, checks its type, then decrypts it.

Here is the entire decompilation: http://www.megafileupload.com/en/file/546477/StarsHostEditor -Source-zip.html

I'm not super familiar with .NET, but it looks easily portable enough into Java or c++.