Guys I just bought ASN for FSX Steam Edition and I ran into some errors. Thankfully I figured out how to fix them after some in-depth forum searching. However, I'd just like to share what solved the problem for me, because it isn't very clearly posted around.
I kept getting the "Cannot control ambient weather" error which lead to a ASN crash. I tried to exclude ASN and some of the .dlls from Microsoft Security Essentials, but kept getting the error. So I read and found that I had to go and edit the dml.xll file in the folder:
C:\Users\(username)\AppData\Roaming\Microsoft\FSX-SE
Right click, edit, and then add the following:
<Launch.Addon>
<Name>as_connect</Name>
<Disabled>False</Disabled>
<Path>as_srv\as_btstrp.dll</Path>
</Launch.Addon>
between
</Launch.Addon>
</SimBase.Document>