Its not problem with Scandinavia DLC
Yust downgrade game and all will be ok, i think
1) Go to your Steam library
2) Right click Euro Truck Simulator 2 and select Properties
3) Click betas tab and select "temporary_1_18_01-for incompatible mods"
4) Let steam update download, and launch multiplayer
Good luck & have fun
http://forum.ets2mp.com/index.php?/topic/15944-fatal-error-solution-scs-released-a-hotfix/