Sorry but there's something wrong with your installation
The disappearing trailer is one of SCS inventions for copyright protection (game thinks your version is "illegal")
Please, I am not saying your version might be illegal but the game engine thinks it is for some weird reason
You could have used a cracked version earlier or If out of luck you have bought a 2nd hand game which turns out to be a cracked version
Also please read this thread on the SCS forum
http://forum.scssoft.com/viewtopic.php?f=8&t=21803
You could erase all copies of ETS2 and do a reinstall as suggested in the thread this could do the trick
Otherwise post your question inlcuding game log on the SCS forum (Technical problems)
http://forum.scssoft.com/viewforum.php?f=8
hth /Peter