I think a couple of players here maybe experiencing some mod conflicts or maybe incorrect load order. Not sure but it seems from the above posts that this could be the case. Make sure if using mods, especially map mods, to load them in the order given in the info that comes with the mod.
I always put map mods at the bottom of the list in the correct order, as per the info. Sound mods are better, I have found, at the top along with physics mods just below those. Truck mods should be below any accessories that go into trucks. This is only what I have found, sometimes it can be a case of 'trial and error' to begin with, to see if things work together. That is the case with most games when modded.