无法更新mysql中的一列

I don't understand why I can't update one column. I have query

$db->setQuery("update #__cars set pro_cars='$itatit' where id='$id'");

It updates fine. If I want to update another column (pro_cars_it) in the same table it doesn't work.

$db->setQuery("update #__cars set pro_cars_it='$itatit' where id='$id'");

I don't have idea why is that. I tried to do both columns at the same time and it's only one table pro_cars updated in the same query.

$db->setQuery("update #__cars set pro_cars='$engtit', pro_cars_it='$itatit' where id='$id'");

Strange. Any idea?