checkbox import problems
The data for importing options needs to be in a single cell. So if your field is COLOUR, then you need a single column for that data in your import file, and you need data such as 


red,blue,orange
red,orange
etc


If you need to concatenate your data you may end up with examples like below, but they should also import fine


red,blue,orange
red,,orange
,blue,orange
,,orange
red,,