When I try to type in a value such as Engine Size or General HP LFS Tune 2.1 crashes. It only happens in the type fields. Using the drop-down menus or the turbo check box works fine. I'm running Vista if that helps and I tried restarting the game. I'm going to switch back to 2.0 for now.
In case no one else has figure this out: if you have the problem with tabbing out to LFS Tweak to find it saying you don't have the s1 or s2 license (might be a vista issue), just right-click on Live For Speed in the taskbar and you should see Tweak return to normal. I discovered this a little while ago and thought I should share.