That is exactly why, cfs3 and all the addons dont like running under windows 7. Especially multiplayer will not work unless you run it in sp3. If you want to know why or how check the "sticky's" on sim-outhouse.com and .net. There are instructional video's on how to get everything working the way it should.
hi have you seen the movie Tailwind made on www.sim-outhouse.net, its in the sticky in CFS3 IP Games or go to this youtube link
It should all work if you follow it to the letter.
Also make sure after install you delete the OLEACC.dll
Hope this helps