Export the tablerates.csv file in System Config > Sales > Shipping methods > Table rates. For the Netherlands the format should be like this (unless you use weight or size as well):
NLD,*,,0.0000,10.0000
NLD,*,,80.0000,0.0000
In this example you get free shipping from 80 euros up, and below that you have to pay 10 euros for shipping. For province the setting should be *, for postcode nothing between the commas. If you use a range for the postcode, that might explain your problem.