One problem that may result when a nation imports more than it exports is

Lower GDP (Gross Domestic Product)

In short, this means that the nation's economy would become dominated by other countries and jobs would be outsourced to cheaper nations, thus increasing the unemployment rate. (just look at America and you can see this in play)

One problem that may occur when a nation imports more than it exports is that the country might have trouble securing foreign currency reserves necessary to buy vital resources such as oil. if you give out more that you take you will slowly run out