Actually, the
.net framework 3.5 sp1 is already shipped with windows 7 as a component, so that may be the issue. Generally you would not have to install .net 3.5 sp1 at all on windows 7, as it is supposed to be there just out of the box. In your case, apparently that was either uninstalled or else got corrupted in some way.
In Windows 7, to manage components you'll need to go under Control Panel, Programs and Features, and then click the "Turn Windows features on or off" on the left side. "Microsoft .NET Framework 3.5.1" is one of the features listed there; you don't need the two "Windows Communication Foundation" items under it, just the Framework itself. You may need to uncheck that box and go through the uninstall process if it's currently checked.
Looking at your error message again, however, I notice there are some subtle differences from what I've seen before. It might have to do with the presence of .NET framework 4.0, I'm not sure. If you can, can you look in your "d:\program files (x86)\steam\steamapps\common\ai war fleet command\" and see if there is an UnhandledExceptions.txt file or anything similar? You might also try doing a "Verify Integrity of Game Cache" on steam, just to be absolutely sure nothing was corrupted.
But when you get an error of that sort, usually it means that the game isn't even getting to run its code because the .NET framework was missing some key DLL. One thing I notice is that it doesn't say that the SlimDX libraries were loaded, so maybe Steam accidentally omitted installing those on your machine; that has happened before, you could try installing them from the prerequisites list there. Usually these error messages are more clear-cut, but the format now that you're on .NET 4.0 is apparently a bit different.
Hope that helps, in summary I think either:
1. The SlimDX prerequisite didn't install.
2. The .NET Framework 3.5.1 component of windows 7 is either not installed or is corrupt.
3. Or something just isn't right with the files Steam delivered, and a simple refresh of the game cache from them would fix it.
As a side note, we're ultimately moving
away from the .NET framework in a couple of months to something with no prerequisites -- because of issues like this. It's been a very rare problem to be sure, something like 1 in 400 customers having any problem and all and with most it's a corrupt install of windows in general, or just Steam skipping a prerequisite at random, but it's still annoying and something we take really seriously. Not that you need to wait until then, one of those three solutions above should be the ticket.
Hope that helps!
