You were probably the victim of the recent attack on Internet Explorer users which came from visiting a certain FS web site.
I believe it is a file called updater.exe that opens a port on your computer. FS used the same port to work with multiplayer. When you quit multiplayer the port which was in a stay open mode caused by updater.exe stayed open (refused to close) and thus FS9 hung.
Run a search for updater.exe. You will have to do the removal in safe mode or DOS mode as it's always in use in Windows and you can't delete something that is in use.
I no longer have the problem.
Jim
